644977 has 2 divisors, whose sum is σ = 644978. Its totient is φ = 644976.

The previous prime is 644951. The next prime is 644999. The reversal of 644977 is 779446.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 571536 + 73441 = 756^2 + 271^2 .

It is a cyclic number.

It is not a de Polignac number, because 644977 - 2¹⁹ = 120689 is a prime.

It is a Chen prime.

It is an Ulam number.

It is not a weakly prime, because it can be changed into another prime (644377) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322488 + 322489.

It is an arithmetic number, because the mean of its divisors is an integer number (322489).

2⁶⁴⁴⁹⁷⁷ is an apocalyptic number.

It is an amenable number.

644977 is a deficient number, since it is larger than the sum of its proper divisors (1).

644977 is an equidigital number, since it uses as much as digits as its factorization.

644977 is an evil number, because the sum of its binary digits is even.

The product of its digits is 42336, while the sum is 37.

The square root of 644977 is about 803.1046009083. The cubic root of 644977 is about 86.4001989736.

It can be divided in two parts, 64 and 4977, that added together give a square (5041 = 71²).

The spelling of 644977 in words is "six hundred forty-four thousand, nine hundred seventy-seven".