645544312531 has 16 divisors (see below), whose sum is σ = 697465728000. Its totient is φ = 595548220608.

The previous prime is 645544312507. The next prime is 645544312577. The reversal of 645544312531 is 135213445546.

It is a cyclic number.

It is not a de Polignac number, because 645544312531 - 2⁹ = 645544312019 is a prime.

It is a super-2 number, since 2×645544312531² (a number of 24 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (645544312631) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1638610 + ... + 1994023.

It is an arithmetic number, because the mean of its divisors is an integer number (43591608000).

Almost surely, 2^645544312531 is an apocalyptic number.

645544312531 is a deficient number, since it is larger than the sum of its proper divisors (51921415469).

645544312531 is a wasteful number, since it uses less digits than its factorization.

645544312531 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3632898.

The product of its digits is 864000, while the sum is 43.

The spelling of 645544312531 in words is "six hundred forty-five billion, five hundred forty-four million, three hundred twelve thousand, five hundred thirty-one".