21897579 has 8 divisors (see below), whose sum is σ = 31851072. Its totient is φ = 13271240.

The previous prime is 21897569. The next prime is 21897611. The reversal of 21897579 is 97579812.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21897579 - 2¹² = 21893483 is a prime.

It is a super-2 number, since 2×21897579² = 959007932122482, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21897509) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 331749 + ... + 331814.

It is an arithmetic number, because the mean of its divisors is an integer number (3981384).

Almost surely, 2^21897579 is an apocalyptic number.

21897579 is a deficient number, since it is larger than the sum of its proper divisors (9953493).

21897579 is a wasteful number, since it uses less digits than its factorization.

21897579 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 663577.

The product of its digits is 317520, while the sum is 48.

The square root of 21897579 is about 4679.4849075513. The cubic root of 21897579 is about 279.7684267280.

The spelling of 21897579 in words is "twenty-one million, eight hundred ninety-seven thousand, five hundred seventy-nine".