21858979 has 2 divisors, whose sum is σ = 21858980. Its totient is φ = 21858978.

The previous prime is 21858931. The next prime is 21858989. The reversal of 21858979 is 97985812.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21858979 - 2²³ = 13470371 is a prime.

It is a super-3 number, since 3×21858979³ (a number of 23 digits) contains 333 as substring.

It is not a weakly prime, because it can be changed into another prime (21858929) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10929489 + 10929490.

It is an arithmetic number, because the mean of its divisors is an integer number (10929490).

Almost surely, 2^21858979 is an apocalyptic number.

21858979 is a deficient number, since it is larger than the sum of its proper divisors (1).

21858979 is an equidigital number, since it uses as much as digits as its factorization.

21858979 is an evil number, because the sum of its binary digits is even.

The product of its digits is 362880, while the sum is 49.

The square root of 21858979 is about 4675.3587028163. The cubic root of 21858979 is about 279.6039425956.

The spelling of 21858979 in words is "twenty-one million, eight hundred fifty-eight thousand, nine hundred seventy-nine".