18491921 has 16 divisors (see below), whose sum is σ = 22373760. Its totient is φ = 14929920.

The previous prime is 18491917. The next prime is 18491927. The reversal of 18491921 is 12919481.

18491921 is nontrivially palindromic in base 16.

It is a cyclic number.

It is not a de Polignac number, because 18491921 - 2² = 18491917 is a prime.

It is a super-2 number, since 2×18491921² = 683902284540482, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (18491927) 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, 33911 + ... + 34451.

It is an arithmetic number, because the mean of its divisors is an integer number (1398360).

Almost surely, 2^18491921 is an apocalyptic number.

It is an amenable number.

18491921 is a deficient number, since it is larger than the sum of its proper divisors (3881839).

18491921 is a wasteful number, since it uses less digits than its factorization.

18491921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 824.

The product of its digits is 5184, while the sum is 35.

The square root of 18491921 is about 4300.2233662916. The cubic root of 18491921 is about 264.4401185192.

The spelling of 18491921 in words is "eighteen million, four hundred ninety-one thousand, nine hundred twenty-one".