645027921 has 32 divisors (see below), whose sum is σ = 972491520. Its totient is φ = 422485632.

The previous prime is 645027871. The next prime is 645027937. The reversal of 645027921 is 129720546.

645027921 is a `hidden beast` number, since 64 + 502 + 7 + 92 + 1 = 666.

It is not a de Polignac number, because 645027921 - 2⁶ = 645027857 is a prime.

It is a super-2 number, since 2×645027921² = 832122037739164482, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (645027221) 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 31 ways as a sum of consecutive naturals, for example, 380151 + ... + 381843.

It is an arithmetic number, because the mean of its divisors is an integer number (30390360).

Almost surely, 2^645027921 is an apocalyptic number.

It is an amenable number.

645027921 is a deficient number, since it is larger than the sum of its proper divisors (327463599).

645027921 is a wasteful number, since it uses less digits than its factorization.

645027921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1942 (or 1936 counting only the distinct ones).

The product of its (nonzero) digits is 30240, while the sum is 36.

The square root of 645027921 is about 25397.3998866026. The cubic root of 645027921 is about 864.0247268193.

The spelling of 645027921 in words is "six hundred forty-five million, twenty-seven thousand, nine hundred twenty-one".