21479809 has 8 divisors (see below), whose sum is σ = 23300480. Its totient is φ = 19683216.

The previous prime is 21479779. The next prime is 21479839. The reversal of 21479809 is 90897412.

It is an interprime number because it is at equal distance from previous prime (21479779) and next prime (21479839).

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21479809 - 2²³ = 13091201 is a prime.

It is a super-2 number, since 2×21479809² = 922764389352962, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21479839) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 4137 + ... + 7750.

It is an arithmetic number, because the mean of its divisors is an integer number (2912560).

Almost surely, 2^21479809 is an apocalyptic number.

It is an amenable number.

21479809 is a deficient number, since it is larger than the sum of its proper divisors (1820671).

21479809 is a wasteful number, since it uses less digits than its factorization.

21479809 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12039.

The product of its (nonzero) digits is 36288, while the sum is 40.

The square root of 21479809 is about 4634.6314848108. The cubic root of 21479809 is about 277.9778159756.

The spelling of 21479809 in words is "twenty-one million, four hundred seventy-nine thousand, eight hundred nine".