644721154 has 24 divisors (see below), whose sum is σ = 1214849664. Its totient is φ = 251189400.

The previous prime is 644721149. The next prime is 644721163. The reversal of 644721154 is 451127446.

It is an unprimeable number.

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, 188602 + ... + 191989.

It is an arithmetic number, because the mean of its divisors is an integer number (50618736).

Almost surely, 2^644721154 is an apocalyptic number.

644721154 is a deficient number, since it is larger than the sum of its proper divisors (570128510).

644721154 is a wasteful number, since it uses less digits than its factorization.

644721154 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 380622 (or 380611 counting only the distinct ones).

The product of its digits is 26880, while the sum is 34.

The square root of 644721154 is about 25391.3598296743. The cubic root of 644721154 is about 863.8877320761.

The spelling of 644721154 in words is "six hundred forty-four million, seven hundred twenty-one thousand, one hundred fifty-four".