661320637 has 2 divisors, whose sum is σ = 661320638. Its totient is φ = 661320636.

The previous prime is 661320599. The next prime is 661320659. The reversal of 661320637 is 736023166.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 643839876 + 17480761 = 25374^2 + 4181^2 .

It is a cyclic number.

It is not a de Polignac number, because 661320637 - 2¹¹ = 661318589 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (631320637) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 330660318 + 330660319.

It is an arithmetic number, because the mean of its divisors is an integer number (330660319).

Almost surely, 2^661320637 is an apocalyptic number.

It is an amenable number.

661320637 is a deficient number, since it is larger than the sum of its proper divisors (1).

661320637 is an equidigital number, since it uses as much as digits as its factorization.

661320637 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 27216, while the sum is 34.

The square root of 661320637 is about 25716.1551752979. The cubic root of 661320637 is about 871.2391014996.

The spelling of 661320637 in words is "six hundred sixty-one million, three hundred twenty thousand, six hundred thirty-seven".