661011557 has 2 divisors, whose sum is σ = 661011558. Its totient is φ = 661011556.

The previous prime is 661011509. The next prime is 661011583. The reversal of 661011557 is 755110166.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 660181636 + 829921 = 25694^2 + 911^2 .

It is a cyclic number.

It is not a de Polignac number, because 661011557 - 2¹⁶ = 660946021 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (661011257) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 330505778 + 330505779.

It is an arithmetic number, because the mean of its divisors is an integer number (330505779).

Almost surely, 2^661011557 is an apocalyptic number.

It is an amenable number.

661011557 is a deficient number, since it is larger than the sum of its proper divisors (1).

661011557 is an equidigital number, since it uses as much as digits as its factorization.

661011557 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 6300, while the sum is 32.

The square root of 661011557 is about 25710.1450209834. The cubic root of 661011557 is about 871.1033506356.

The spelling of 661011557 in words is "six hundred sixty-one million, eleven thousand, five hundred fifty-seven".