644977873 has 2 divisors, whose sum is σ = 644977874. Its totient is φ = 644977872.

The previous prime is 644977843. The next prime is 644977901. The reversal of 644977873 is 378779446.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 532363329 + 112614544 = 23073^2 + 10612^2 .

It is a cyclic number.

It is not a de Polignac number, because 644977873 - 2¹⁷ = 644846801 is a prime.

It is a super-3 number, since 3×644977873³ (a number of 27 digits) contains 333 as substring.

It is not a weakly prime, because it can be changed into another prime (644977843) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322488936 + 322488937.

It is an arithmetic number, because the mean of its divisors is an integer number (322488937).

Almost surely, 2^644977873 is an apocalyptic number.

It is an amenable number.

644977873 is a deficient number, since it is larger than the sum of its proper divisors (1).

644977873 is an equidigital number, since it uses as much as digits as its factorization.

644977873 is an evil number, because the sum of its binary digits is even.

The product of its digits is 7112448, while the sum is 55.

The square root of 644977873 is about 25396.4145697774. The cubic root of 644977873 is about 864.0023795552.

The spelling of 644977873 in words is "six hundred forty-four million, nine hundred seventy-seven thousand, eight hundred seventy-three".