661136251 has 4 divisors (see below), whose sum is σ = 669101832. Its totient is φ = 653170672.

The previous prime is 661136243. The next prime is 661136261. The reversal of 661136251 is 152631166.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 661136251 - 2³ = 661136243 is a prime.

It is a super-2 number, since 2×661136251² = 874202284772670002, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (661136221) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3982666 + ... + 3982831.

It is an arithmetic number, because the mean of its divisors is an integer number (167275458).

Almost surely, 2^661136251 is an apocalyptic number.

661136251 is a deficient number, since it is larger than the sum of its proper divisors (7965581).

661136251 is an equidigital number, since it uses as much as digits as its factorization.

661136251 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7965580.

The product of its digits is 6480, while the sum is 31.

The square root of 661136251 is about 25712.5699026760. The cubic root of 661136251 is about 871.1581225129.

The spelling of 661136251 in words is "six hundred sixty-one million, one hundred thirty-six thousand, two hundred fifty-one".