66821520 has 80 divisors (see below), whose sum is σ = 207933120. Its totient is φ = 17751552.

The previous prime is 66821479. The next prime is 66821551. The reversal of 66821520 is 2512866.

It is a tau number, because it is divible by the number of its divisors (80).

It is a super-2 number, since 2×66821520² = 8930231070220800, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (30).

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 121887 + ... + 122433.

It is an arithmetic number, because the mean of its divisors is an integer number (2599164).

Almost surely, 2^66821520 is an apocalyptic number.

66821520 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 66821520, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (103966560).

66821520 is an abundant number, since it is smaller than the sum of its proper divisors (141111600).

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

66821520 is a wasteful number, since it uses less digits than its factorization.

66821520 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1072 (or 1066 counting only the distinct ones).

The product of its (nonzero) digits is 5760, while the sum is 30.

The square root of 66821520 is about 8174.4431002974. The cubic root of 66821520 is about 405.7938400216.

The spelling of 66821520 in words is "sixty-six million, eight hundred twenty-one thousand, five hundred twenty".