21624779 has 4 divisors (see below), whose sum is σ = 23590680. Its totient is φ = 19658880.

The previous prime is 21624769. The next prime is 21624781. The reversal of 21624779 is 97742612.

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 21624779 - 2²⁰ = 20576203 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21624769) 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, 982934 + ... + 982955.

It is an arithmetic number, because the mean of its divisors is an integer number (5897670).

Almost surely, 2^21624779 is an apocalyptic number.

21624779 is a deficient number, since it is larger than the sum of its proper divisors (1965901).

21624779 is a wasteful number, since it uses less digits than its factorization.

21624779 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1965900.

The product of its digits is 42336, while the sum is 38.

The square root of 21624779 is about 4650.2450473066. The cubic root of 21624779 is about 278.6017836995.

The spelling of 21624779 in words is "twenty-one million, six hundred twenty-four thousand, seven hundred seventy-nine".