21808497 has 8 divisors (see below), whose sum is σ = 29143456. Its totient is φ = 14506272.

The previous prime is 21808489. The next prime is 21808519. The reversal of 21808497 is 79480812.

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

It is not a de Polignac number, because 21808497 - 2³ = 21808489 is a prime.

It is a super-2 number, since 2×21808497² = 951221082798018, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21808417) 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, 6583 + ... + 9324.

It is an arithmetic number, because the mean of its divisors is an integer number (3642932).

Almost surely, 2^21808497 is an apocalyptic number.

It is an amenable number.

21808497 is a deficient number, since it is larger than the sum of its proper divisors (7334959).

21808497 is a wasteful number, since it uses less digits than its factorization.

21808497 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 16367.

The product of its (nonzero) digits is 32256, while the sum is 39.

The square root of 21808497 is about 4669.9568520491. The cubic root of 21808497 is about 279.3885338448.

The spelling of 21808497 in words is "twenty-one million, eight hundred eight thousand, four hundred ninety-seven".