661131257 has 2 divisors, whose sum is σ = 661131258. Its totient is φ = 661131256.

The previous prime is 661131223. The next prime is 661131283. The reversal of 661131257 is 752131166.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 357361216 + 303770041 = 18904^2 + 17429^2 .

It is a cyclic number.

It is not a de Polignac number, because 661131257 - 2²² = 656936953 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (661131287) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 330565628 + 330565629.

It is an arithmetic number, because the mean of its divisors is an integer number (330565629).

Almost surely, 2^661131257 is an apocalyptic number.

It is an amenable number.

661131257 is a deficient number, since it is larger than the sum of its proper divisors (1).

661131257 is an equidigital number, since it uses as much as digits as its factorization.

661131257 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 7560, while the sum is 32.

The square root of 661131257 is about 25712.4727904572. The cubic root of 661131257 is about 871.1559290293.

Subtracting 661131257 from its reverse (752131166), we obtain a palindrome (90999909).

The spelling of 661131257 in words is "six hundred sixty-one million, one hundred thirty-one thousand, two hundred fifty-seven".