644977901 has 2 divisors, whose sum is σ = 644977902. Its totient is φ = 644977900.

The previous prime is 644977873. The next prime is 644977919. The reversal of 644977901 is 109779446.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 604668100 + 40309801 = 24590^2 + 6349^2 .

It is a cyclic number.

It is not a de Polignac number, because 644977901 - 2²² = 640783597 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (644977301) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322488950 + 322488951.

It is an arithmetic number, because the mean of its divisors is an integer number (322488951).

Almost surely, 2^644977901 is an apocalyptic number.

It is an amenable number.

644977901 is a deficient number, since it is larger than the sum of its proper divisors (1).

644977901 is an equidigital number, since it uses as much as digits as its factorization.

644977901 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 381024, while the sum is 47.

The square root of 644977901 is about 25396.4151210363. The cubic root of 644977901 is about 864.0023920580.

The spelling of 644977901 in words is "six hundred forty-four million, nine hundred seventy-seven thousand, nine hundred one".