644249901 has 16 divisors (see below), whose sum is σ = 920493504. Its totient is φ = 399362304.

The previous prime is 644249897. The next prime is 644249909. The reversal of 644249901 is 109942446.

It is not a de Polignac number, because 644249901 - 2² = 644249897 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 644249901.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644249909) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 71866 + ... + 80331.

It is an arithmetic number, because the mean of its divisors is an integer number (57530844).

Almost surely, 2^644249901 is an apocalyptic number.

It is an amenable number.

644249901 is a deficient number, since it is larger than the sum of its proper divisors (276243603).

644249901 is a wasteful number, since it uses less digits than its factorization.

644249901 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 152300.

The product of its (nonzero) digits is 62208, while the sum is 39.

The square root of 644249901 is about 25382.0783427993. The cubic root of 644249901 is about 863.6771971732.

The spelling of 644249901 in words is "six hundred forty-four million, two hundred forty-nine thousand, nine hundred one".