645063021 has 20 divisors (see below), whose sum is σ = 964309500. Its totient is φ = 429731136.

The previous prime is 645063019. The next prime is 645063031. The reversal of 645063021 is 120360546.

645063021 is a `hidden beast` number, since 6 + 4 + 5 + 0 + 630 + 21 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 212838921 + 432224100 = 14589^2 + 20790^2 .

It is not a de Polignac number, because 645063021 - 2¹ = 645063019 is a prime.

It is a super-2 number, since 2×645063021² = 832212602123292882, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (645063031) by changing a digit.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 185305 + ... + 188753.

It is an arithmetic number, because the mean of its divisors is an integer number (48215475).

Almost surely, 2^645063021 is an apocalyptic number.

It is an amenable number.

645063021 is a deficient number, since it is larger than the sum of its proper divisors (319246479).

645063021 is a wasteful number, since it uses less digits than its factorization.

645063021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5770 (or 5761 counting only the distinct ones).

The product of its (nonzero) digits is 4320, while the sum is 27.

The square root of 645063021 is about 25398.0908928211. The cubic root of 645063021 is about 864.0403988633.

The spelling of 645063021 in words is "six hundred forty-five million, sixty-three thousand, twenty-one".