21627921 has 16 divisors (see below), whose sum is σ = 33021824. Its totient is φ = 12334464.

The previous prime is 21627913. The next prime is 21627923. The reversal of 21627921 is 12972612.

It is not a de Polignac number, because 21627921 - 2³ = 21627913 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21627923) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 20421 + ... + 21453.

It is an arithmetic number, because the mean of its divisors is an integer number (2063864).

Almost surely, 2^21627921 is an apocalyptic number.

21627921 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

It is an amenable number.

21627921 is a deficient number, since it is larger than the sum of its proper divisors (11393903).

21627921 is a wasteful number, since it uses less digits than its factorization.

21627921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2040.

The product of its digits is 3024, while the sum is 30.

The square root of 21627921 is about 4650.5828666953. The cubic root of 21627921 is about 278.6152763138.

The spelling of 21627921 in words is "twenty-one million, six hundred twenty-seven thousand, nine hundred twenty-one".