64817820 has 72 divisors (see below), whose sum is σ = 203911344. Its totient is φ = 17283456.

The previous prime is 64817803. The next prime is 64817827. The reversal of 64817820 is 2871846.

64817820 is a `hidden beast` number, since 648 + 1 + 7 + 8 + 2 + 0 = 666.

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 (64817827) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 1809 + ... + 11528.

It is an arithmetic number, because the mean of its divisors is an integer number (2832102).

Almost surely, 2^64817820 is an apocalyptic number.

64817820 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 64817820, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (101955672).

64817820 is an abundant number, since it is smaller than the sum of its proper divisors (139093524).

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

64817820 is a wasteful number, since it uses less digits than its factorization.

64817820 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 13361 (or 13347 counting only the distinct ones).

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

The square root of 64817820 is about 8050.9514965624. The cubic root of 64817820 is about 401.6965854870.

The spelling of 64817820 in words is "sixty-four million, eight hundred seventeen thousand, eight hundred twenty".