639616057621 has 2 divisors, whose sum is σ = 639616057622. Its totient is φ = 639616057620.

The previous prime is 639616057571. The next prime is 639616057651. The reversal of 639616057621 is 126750616936.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 595814172100 + 43801885521 = 771890^2 + 209289^2 .

It is a cyclic number.

It is not a de Polignac number, because 639616057621 - 2⁹ = 639616057109 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (639616057651) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 319808028810 + 319808028811.

It is an arithmetic number, because the mean of its divisors is an integer number (319808028811).

Almost surely, 2^639616057621 is an apocalyptic number.

It is an amenable number.

639616057621 is a deficient number, since it is larger than the sum of its proper divisors (1).

639616057621 is an equidigital number, since it uses as much as digits as its factorization.

639616057621 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 2449440, while the sum is 52.

The spelling of 639616057621 in words is "six hundred thirty-nine billion, six hundred sixteen million, fifty-seven thousand, six hundred twenty-one".