66921720 has 64 divisors (see below), whose sum is σ = 209502720. Its totient is φ = 17069184.

The previous prime is 66921719. The next prime is 66921733. The reversal of 66921720 is 2712966.

It is a congruent number.

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, 9364 + ... + 14883.

It is an arithmetic number, because the mean of its divisors is an integer number (3273480).

Almost surely, 2^66921720 is an apocalyptic number.

66921720 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

66921720 is an abundant number, since it is smaller than the sum of its proper divisors (142581000).

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

66921720 is a wasteful number, since it uses less digits than its factorization.

66921720 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 24284 (or 24280 counting only the distinct ones).

The product of its (nonzero) digits is 9072, while the sum is 33.

The square root of 66921720 is about 8180.5696623157. The cubic root of 66921720 is about 405.9965702995.

The spelling of 66921720 in words is "sixty-six million, nine hundred twenty-one thousand, seven hundred twenty".