18400031 has 4 divisors (see below), whose sum is σ = 19815432. Its totient is φ = 16984632.

The previous prime is 18400013. The next prime is 18400049. The reversal of 18400031 is 13000481.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 13000481 = 13 ⋅1000037.

It is an interprime number because it is at equal distance from previous prime (18400013) and next prime (18400049).

It is a cyclic number.

It is not a de Polignac number, because 18400031 - 2¹⁸ = 18137887 is a prime.

It is a super-2 number, since 2×18400031² = 677122281601922, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 18399982 and 18400009.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18400051) 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, 707681 + ... + 707706.

It is an arithmetic number, because the mean of its divisors is an integer number (4953858).

Almost surely, 2^18400031 is an apocalyptic number.

18400031 is a deficient number, since it is larger than the sum of its proper divisors (1415401).

18400031 is a wasteful number, since it uses less digits than its factorization.

18400031 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1415400.

The product of its (nonzero) digits is 96, while the sum is 17.

The square root of 18400031 is about 4289.5257313601. The cubic root of 18400031 is about 264.0013726207.

The spelling of 18400031 in words is "eighteen million, four hundred thousand, thirty-one".