644740026 has 16 divisors (see below), whose sum is σ = 1473691584. Its totient is φ = 184211424.

The previous prime is 644740013. The next prime is 644740039. The reversal of 644740026 is 620047446.

It is an interprime number because it is at equal distance from previous prime (644740013) and next prime (644740039).

It is a super-2 number, since 2×644740026² = 831379402252961352, which contains 22 as substring.

It is an unprimeable number.

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 7 ways as a sum of consecutive naturals, for example, 7675435 + ... + 7675518.

It is an arithmetic number, because the mean of its divisors is an integer number (92105724).

Almost surely, 2^644740026 is an apocalyptic number.

644740026 is an abundant number, since it is smaller than the sum of its proper divisors (828951558).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

644740026 is a wasteful number, since it uses less digits than its factorization.

644740026 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 15350965.

The product of its (nonzero) digits is 32256, while the sum is 33.

The square root of 644740026 is about 25391.7314494305. The cubic root of 644740026 is about 863.8961611104.

The spelling of 644740026 in words is "six hundred forty-four million, seven hundred forty thousand, twenty-six".