645315561 has 48 divisors (see below), whose sum is σ = 1054789632. Its totient is φ = 376639200.

The previous prime is 645315527. The next prime is 645315581. The reversal of 645315561 is 165513546.

645315561 is a `hidden beast` number, since 64 + 5 + 31 + 5 + 561 = 666.

It is not a de Polignac number, because 645315561 - 2¹⁸ = 645053417 is a prime.

It is a hoax number, since the sum of its digits (36) coincides with the sum of the digits of its distinct prime factors.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (645315581) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 868156 + ... + 868898.

It is an arithmetic number, because the mean of its divisors is an integer number (21974784).

Almost surely, 2^645315561 is an apocalyptic number.

It is an amenable number.

645315561 is a deficient number, since it is larger than the sum of its proper divisors (409474071).

645315561 is a wasteful number, since it uses less digits than its factorization.

645315561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1074 (or 1071 counting only the distinct ones).

The product of its digits is 54000, while the sum is 36.

The square root of 645315561 is about 25403.0620398408. The cubic root of 645315561 is about 864.1531404539.

The spelling of 645315561 in words is "six hundred forty-five million, three hundred fifteen thousand, five hundred sixty-one".