1216505631 has 8 divisors (see below), whose sum is σ = 1769462784. Its totient is φ = 737276120.

The previous prime is 1216505623. The next prime is 1216505639. The reversal of 1216505631 is 1365056121.

It is an interprime number because it is at equal distance from previous prime (1216505623) and next prime (1216505639).

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 1216505631 - 2³ = 1216505623 is a prime.

It is a super-2 number, since 2×1216505631² = 2959771900509416322, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1216505639) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 18431871 + ... + 18431936.

It is an arithmetic number, because the mean of its divisors is an integer number (221182848).

Almost surely, 2^1216505631 is an apocalyptic number.

1216505631 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

1216505631 is a deficient number, since it is larger than the sum of its proper divisors (552957153).

1216505631 is a wasteful number, since it uses less digits than its factorization.

1216505631 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 36863821.

The product of its (nonzero) digits is 5400, while the sum is 30.

The square root of 1216505631 is about 34878.4407765026. The cubic root of 1216505631 is about 1067.5085805006.

The spelling of 1216505631 in words is "one billion, two hundred sixteen million, five hundred five thousand, six hundred thirty-one".