21420923 has 16 divisors (see below), whose sum is σ = 23358720. Its totient is φ = 19577376.

The previous prime is 21420887. The next prime is 21420941. The reversal of 21420923 is 32902412.

It is a cyclic number.

It is not a de Polignac number, because 21420923 - 2⁶ = 21420859 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21420023) 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, 128186 + ... + 128352.

It is an arithmetic number, because the mean of its divisors is an integer number (1459920).

Almost surely, 2^21420923 is an apocalyptic number.

21420923 is a deficient number, since it is larger than the sum of its proper divisors (1937797).

21420923 is a wasteful number, since it uses less digits than its factorization.

21420923 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 386.

The product of its (nonzero) digits is 864, while the sum is 23.

The square root of 21420923 is about 4628.2743004278. The cubic root of 21420923 is about 277.7235619642.

The spelling of 21420923 in words is "twenty-one million, four hundred twenty thousand, nine hundred twenty-three".