644710761 has 6 divisors (see below), whose sum is σ = 931248890. Its totient is φ = 429807168.

The previous prime is 644710753. The next prime is 644710789. The reversal of 644710761 is 167017446.

644710761 is a `hidden beast` number, since 644 + 7 + 1 + 0 + 7 + 6 + 1 = 666.

It can be written as a sum of positive squares in only one way, i.e., 351787536 + 292923225 = 18756^2 + 17115^2 .

It is not a de Polignac number, because 644710761 - 2³ = 644710753 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (644710721) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 35817256 + ... + 35817273.

Almost surely, 2^644710761 is an apocalyptic number.

It is an amenable number.

644710761 is a deficient number, since it is larger than the sum of its proper divisors (286538129).

644710761 is a wasteful number, since it uses less digits than its factorization.

644710761 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 71634535 (or 71634532 counting only the distinct ones).

The product of its (nonzero) digits is 28224, while the sum is 36.

The square root of 644710761 is about 25391.1551726187. The cubic root of 644710761 is about 863.8830900520.

The spelling of 644710761 in words is "six hundred forty-four million, seven hundred ten thousand, seven hundred sixty-one".