661613957 has 2 divisors, whose sum is σ = 661613958. Its totient is φ = 661613956.

The previous prime is 661613951. The next prime is 661613987. The reversal of 661613957 is 759316166.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 465221761 + 196392196 = 21569^2 + 14014^2 .

It is a cyclic number.

It is not a de Polignac number, because 661613957 - 2⁴ = 661613941 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 (661613951) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 330806978 + 330806979.

It is an arithmetic number, because the mean of its divisors is an integer number (330806979).

Almost surely, 2^661613957 is an apocalyptic number.

It is an amenable number.

661613957 is a deficient number, since it is larger than the sum of its proper divisors (1).

661613957 is an equidigital number, since it uses as much as digits as its factorization.

661613957 is an evil number, because the sum of its binary digits is even.

The product of its digits is 204120, while the sum is 44.

The square root of 661613957 is about 25721.8575728892. The cubic root of 661613957 is about 871.3678913110.

The spelling of 661613957 in words is "six hundred sixty-one million, six hundred thirteen thousand, nine hundred fifty-seven".