21579497 has 18 divisors (see below), whose sum is σ = 24019002. Its totient is φ = 19381824.

The previous prime is 21579491. The next prime is 21579517. The reversal of 21579497 is 79497512.

It can be written as a sum of positive squares in only one way, i.e., 12222016 + 9357481 = 3496^2 + 3059^2 .

It is not a de Polignac number, because 21579497 - 2⁶ = 21579433 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21579491) by changing a digit.

It is a polite number, since it can be written in 17 ways as a sum of consecutive naturals, for example, 190913 + ... + 191025.

It is an arithmetic number, because the mean of its divisors is an integer number (1334389).

Almost surely, 2^21579497 is an apocalyptic number.

It is an amenable number.

21579497 is a deficient number, since it is larger than the sum of its proper divisors (2439505).

21579497 is a wasteful number, since it uses less digits than its factorization.

21579497 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 197 (or 155 counting only the distinct ones).

The product of its digits is 158760, while the sum is 44.

The square root of 21579497 is about 4645.3737201650. The cubic root of 21579497 is about 278.4071849956.

The spelling of 21579497 in words is "twenty-one million, five hundred seventy-nine thousand, four hundred ninety-seven".