21479905 has 4 divisors (see below), whose sum is σ = 25775892. Its totient is φ = 17183920.

The previous prime is 21479881. The next prime is 21479911. The reversal of 21479905 is 50997412.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 5987809 + 15492096 = 2447^2 + 3936^2 .

It is not a de Polignac number, because 21479905 - 2⁵ = 21479873 is a prime.

It is a super-2 number, since 2×21479905² = 922772637618050, which contains 22 as substring.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2147986 + ... + 2147995.

It is an arithmetic number, because the mean of its divisors is an integer number (6443973).

Almost surely, 2^21479905 is an apocalyptic number.

It is an amenable number.

21479905 is a deficient number, since it is larger than the sum of its proper divisors (4295987).

21479905 is an equidigital number, since it uses as much as digits as its factorization.

21479905 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4295986.

The product of its (nonzero) digits is 22680, while the sum is 37.

The square root of 21479905 is about 4634.6418416098. The cubic root of 21479905 is about 277.9782300983.

The spelling of 21479905 in words is "twenty-one million, four hundred seventy-nine thousand, nine hundred five".