644697091 has 12 divisors (see below), whose sum is σ = 657437040. Its totient is φ = 632191680.

The previous prime is 644697083. The next prime is 644697121. The reversal of 644697091 is 190796446.

It is not a de Polignac number, because 644697091 - 2³ = 644697083 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644697041) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 1657125 + ... + 1657513.

It is an arithmetic number, because the mean of its divisors is an integer number (54786420).

Almost surely, 2^644697091 is an apocalyptic number.

644697091 is a deficient number, since it is larger than the sum of its proper divisors (12739949).

644697091 is an equidigital number, since it uses as much as digits as its factorization.

644697091 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 846 (or 773 counting only the distinct ones).

The product of its (nonzero) digits is 326592, while the sum is 46.

The square root of 644697091 is about 25390.8859829664. The cubic root of 644697091 is about 863.8769842828.

The spelling of 644697091 in words is "six hundred forty-four million, six hundred ninety-seven thousand, ninety-one".