661503631 has 2 divisors, whose sum is σ = 661503632. Its totient is φ = 661503630.

The previous prime is 661503613. The next prime is 661503671. The reversal of 661503631 is 136305166.

Together with previous prime (661503613) it forms an Ormiston pair, because they use the same digits, order apart.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 661503631 - 2⁵ = 661503599 is a prime.

It is a super-2 number, since 2×661503631² = 875174107652368322, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 661503593 and 661503602.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (661503671) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 330751815 + 330751816.

It is an arithmetic number, because the mean of its divisors is an integer number (330751816).

Almost surely, 2^661503631 is an apocalyptic number.

661503631 is a deficient number, since it is larger than the sum of its proper divisors (1).

661503631 is an equidigital number, since it uses as much as digits as its factorization.

661503631 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 9720, while the sum is 31.

The square root of 661503631 is about 25719.7128872000. The cubic root of 661503631 is about 871.3194542645.

Adding to 661503631 its reverse (136305166), we get a palindrome (797808797).

The spelling of 661503631 in words is "six hundred sixty-one million, five hundred three thousand, six hundred thirty-one".