661326631 has 4 divisors (see below), whose sum is σ = 755801872. Its totient is φ = 566851392.

The previous prime is 661326619. The next prime is 661326647. The reversal of 661326631 is 136623166.

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 661326631 - 2¹³ = 661318439 is a prime.

It is a super-2 number, since 2×661326631² = 874705825739620322, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (661326031) 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, 47237610 + ... + 47237623.

It is an arithmetic number, because the mean of its divisors is an integer number (188950468).

Almost surely, 2^661326631 is an apocalyptic number.

661326631 is a deficient number, since it is larger than the sum of its proper divisors (94475241).

661326631 is an equidigital number, since it uses as much as digits as its factorization.

661326631 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 94475240.

The product of its digits is 23328, while the sum is 34.

The square root of 661326631 is about 25716.2717165611. The cubic root of 661326631 is about 871.2417337031.

Adding to 661326631 its reverse (136623166), we get a palindrome (797949797).

The spelling of 661326631 in words is "six hundred sixty-one million, three hundred twenty-six thousand, six hundred thirty-one".