661026557 has 2 divisors, whose sum is σ = 661026558. Its totient is φ = 661026556.

The previous prime is 661026539. The next prime is 661026617. The reversal of 661026557 is 755620166.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 546343876 + 114682681 = 23374^2 + 10709^2 .

It is a cyclic number.

It is not a de Polignac number, because 661026557 - 2¹⁴ = 661010173 is a prime.

It is a super-2 number, since 2×661026557² = 873912218118548498, which contains 22 as substring.

It is a Chen prime.

It is equal to p_34336757 and since 661026557 and 34336757 have the same sum of digits, it is a Honaker prime.

It is a self number, because there is not a number n which added to its sum of digits gives 661026557.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (661026257) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 330513278 + 330513279.

It is an arithmetic number, because the mean of its divisors is an integer number (330513279).

Almost surely, 2^661026557 is an apocalyptic number.

It is an amenable number.

661026557 is a deficient number, since it is larger than the sum of its proper divisors (1).

661026557 is an equidigital number, since it uses as much as digits as its factorization.

661026557 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 75600, while the sum is 38.

The square root of 661026557 is about 25710.4367329690. The cubic root of 661026557 is about 871.1099397545.

The spelling of 661026557 in words is "six hundred sixty-one million, twenty-six thousand, five hundred fifty-seven".