644697090 has 32 divisors (see below), whose sum is σ = 1719192960. Its totient is φ = 171919152.

The previous prime is 644697083. The next prime is 644697121. The reversal of 644697090 is 90796446.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1193614 + ... + 1194153.

It is an arithmetic number, because the mean of its divisors is an integer number (53724780).

Almost surely, 2^644697090 is an apocalyptic number.

644697090 is an abundant number, since it is smaller than the sum of its proper divisors (1074495870).

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

644697090 is a wasteful number, since it uses less digits than its factorization.

644697090 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2387783 (or 2387777 counting only the distinct ones).

The product of its (nonzero) digits is 326592, while the sum is 45.

The square root of 644697090 is about 25390.8859632743. The cubic root of 644697090 is about 863.8769838361.

The spelling of 644697090 in words is "six hundred forty-four million, six hundred ninety-seven thousand, ninety".