18261631 has 4 divisors (see below), whose sum is σ = 18561064. Its totient is φ = 17962200.

The previous prime is 18261623. The next prime is 18261637. The reversal of 18261631 is 13616281.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 13616281 = 7 ⋅1945183.

It is a cyclic number.

It is not a de Polignac number, because 18261631 - 2³ = 18261623 is a prime.

It is a super-2 number, since 2×18261631² = 666974333560322, which contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 18261631.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18261637) 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, 149625 + ... + 149746.

It is an arithmetic number, because the mean of its divisors is an integer number (4640266).

Almost surely, 2^18261631 is an apocalyptic number.

18261631 is a deficient number, since it is larger than the sum of its proper divisors (299433).

18261631 is an equidigital number, since it uses as much as digits as its factorization.

18261631 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 299432.

The product of its digits is 1728, while the sum is 28.

The square root of 18261631 is about 4273.3629614158. The cubic root of 18261631 is about 263.3377906988.

The spelling of 18261631 in words is "eighteen million, two hundred sixty-one thousand, six hundred thirty-one".