661957771 has 2 divisors, whose sum is σ = 661957772. Its totient is φ = 661957770.

The previous prime is 661957759. The next prime is 661957817. The reversal of 661957771 is 177759166.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 661957771 - 2¹³ = 661949579 is a prime.

It is not a weakly prime, because it can be changed into another prime (661957721) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 330978885 + 330978886.

It is an arithmetic number, because the mean of its divisors is an integer number (330978886).

Almost surely, 2^661957771 is an apocalyptic number.

661957771 is a deficient number, since it is larger than the sum of its proper divisors (1).

661957771 is an equidigital number, since it uses as much as digits as its factorization.

661957771 is an evil number, because the sum of its binary digits is even.

The product of its digits is 555660, while the sum is 49.

The square root of 661957771 is about 25728.5400091027. The cubic root of 661957771 is about 871.5188033836.

The spelling of 661957771 in words is "six hundred sixty-one million, nine hundred fifty-seven thousand, seven hundred seventy-one".