18121631 has 16 divisors (see below), whose sum is σ = 21143808. Its totient is φ = 15364800.

The previous prime is 18121613. The next prime is 18121633. The reversal of 18121631 is 13612181.

It is not a de Polignac number, because 18121631 - 2⁶ = 18121567 is a prime.

It is a super-2 number, since 2×18121631² = 656787020200322, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (23).

It is a junction number, because it is equal to n+sod(n) for n = 18121597 and 18121606.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18121633) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 9500 + ... + 11246.

It is an arithmetic number, because the mean of its divisors is an integer number (1321488).

Almost surely, 2^18121631 is an apocalyptic number.

18121631 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

18121631 is a deficient number, since it is larger than the sum of its proper divisors (3022177).

18121631 is a wasteful number, since it uses less digits than its factorization.

18121631 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1822.

The product of its digits is 288, while the sum is 23.

The square root of 18121631 is about 4256.9509041097. The cubic root of 18121631 is about 262.6631173632.

It can be divided in two parts, 1812 and 1631, that added together give a palindrome (3443).

The spelling of 18121631 in words is "eighteen million, one hundred twenty-one thousand, six hundred thirty-one".