21554979 has 16 divisors (see below), whose sum is σ = 30803712. Its totient is φ = 13372128.

The previous prime is 21554969. The next prime is 21554983. The reversal of 21554979 is 97945512.

It is not a de Polignac number, because 21554979 - 2⁵ = 21554947 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21554979.

It is not an unprimeable number, because it can be changed into a prime (21554969) 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, 1669 + ... + 6774.

It is an arithmetic number, because the mean of its divisors is an integer number (1925232).

Almost surely, 2^21554979 is an apocalyptic number.

21554979 is a deficient number, since it is larger than the sum of its proper divisors (9248733).

21554979 is a wasteful number, since it uses less digits than its factorization.

21554979 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8506.

The product of its digits is 113400, while the sum is 42.

The square root of 21554979 is about 4642.7340005648. The cubic root of 21554979 is about 278.3017056424.

The spelling of 21554979 in words is "twenty-one million, five hundred fifty-four thousand, nine hundred seventy-nine".