64821780 has 72 divisors (see below), whose sum is σ = 201961032. Its totient is φ = 16816896.

The previous prime is 64821767. The next prime is 64821781. The reversal of 64821780 is 8712846.

64821780 is a `hidden beast` number, since 6 + 482 + 178 + 0 = 666.

64821780 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It can be written as a sum of positive squares in 4 ways, for example, as 30669444 + 34152336 = 5538^2 + 5844^2 .

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (64821781) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 1794 + ... + 11526.

Almost surely, 2^64821780 is an apocalyptic number.

64821780 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 64821780, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (100980516).

64821780 is an abundant number, since it is smaller than the sum of its proper divisors (137139252).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

64821780 is a wasteful number, since it uses less digits than its factorization.

64821780 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9785 (or 9780 counting only the distinct ones).

The product of its (nonzero) digits is 21504, while the sum is 36.

The square root of 64821780 is about 8051.1974264702. The cubic root of 64821780 is about 401.7047657790.

The spelling of 64821780 in words is "sixty-four million, eight hundred twenty-one thousand, seven hundred eighty".