21718879 has 16 divisors (see below), whose sum is σ = 27596800. Its totient is φ = 16627680.

The previous prime is 21718871. The next prime is 21718891. The reversal of 21718879 is 97881712.

It is a happy number.

It is a cyclic number.

It is not a de Polignac number, because 21718879 - 2³ = 21718871 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21718871) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1029 + ... + 6670.

It is an arithmetic number, because the mean of its divisors is an integer number (1724800).

Almost surely, 2^21718879 is an apocalyptic number.

21718879 is a deficient number, since it is larger than the sum of its proper divisors (5877921).

21718879 is a wasteful number, since it uses less digits than its factorization.

21718879 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7750.

The product of its digits is 56448, while the sum is 43.

The square root of 21718879 is about 4660.3518107542. The cubic root of 21718879 is about 279.0053098684.

The spelling of 21718879 in words is "twenty-one million, seven hundred eighteen thousand, eight hundred seventy-nine".