20181921 has 16 divisors (see below), whose sum is σ = 27825600. Its totient is φ = 13003200.

The previous prime is 20181859. The next prime is 20181937. The reversal of 20181921 is 12918102.

It is not a de Polignac number, because 20181921 - 2⁷ = 20181793 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 20181891 and 20181900.

It is not an unprimeable number, because it can be changed into a prime (20181121) 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, 12255 + ... + 13803.

It is an arithmetic number, because the mean of its divisors is an integer number (1739100).

Almost surely, 2^20181921 is an apocalyptic number.

It is an amenable number.

20181921 is a deficient number, since it is larger than the sum of its proper divisors (7643679).

20181921 is a wasteful number, since it uses less digits than its factorization.

20181921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1696.

The product of its (nonzero) digits is 288, while the sum is 24.

The square root of 20181921 is about 4492.4292982750. The cubic root of 20181921 is about 272.2622947410.

The spelling of 20181921 in words is "twenty million, one hundred eighty-one thousand, nine hundred twenty-one".