644969440531 has 16 divisors (see below), whose sum is σ = 710778317760. Its totient is φ = 581572368000.

The previous prime is 644969440523. The next prime is 644969440651. The reversal of 644969440531 is 135044969446.

It is not a de Polignac number, because 644969440531 - 2³ = 644969440523 is a prime.

It is a super-2 number, since 2×644969440531² (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 (644969470531) 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, 1886095 + ... + 2201656.

It is an arithmetic number, because the mean of its divisors is an integer number (44423644860).

Almost surely, 2^644969440531 is an apocalyptic number.

644969440531 is a deficient number, since it is larger than the sum of its proper divisors (65808877229).

644969440531 is a wasteful number, since it uses less digits than its factorization.

644969440531 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4088046.

The product of its (nonzero) digits is 11197440, while the sum is 55.

The spelling of 644969440531 in words is "six hundred forty-four billion, nine hundred sixty-nine million, four hundred forty thousand, five hundred thirty-one".