21564479 has 4 divisors (see below), whose sum is σ = 21824376. Its totient is φ = 21304584.

The previous prime is 21564463. The next prime is 21564497. The reversal of 21564479 is 97446512.

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

It is a cyclic number.

It is not a de Polignac number, because 21564479 - 2⁴ = 21564463 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21564079) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 129824 + ... + 129989.

It is an arithmetic number, because the mean of its divisors is an integer number (5456094).

Almost surely, 2^21564479 is an apocalyptic number.

21564479 is a deficient number, since it is larger than the sum of its proper divisors (259897).

21564479 is an equidigital number, since it uses as much as digits as its factorization.

21564479 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 259896.

The product of its digits is 60480, while the sum is 38.

The square root of 21564479 is about 4643.7569919194. The cubic root of 21564479 is about 278.3425852598.

The spelling of 21564479 in words is "twenty-one million, five hundred sixty-four thousand, four hundred seventy-nine".