21655497 has 16 divisors (see below), whose sum is σ = 30827520. Its totient is φ = 13482000.

The previous prime is 21655493. The next prime is 21655507. The reversal of 21655497 is 79455612.

It is not a de Polignac number, because 21655497 - 2² = 21655493 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21655493) 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, 1372 + ... + 6722.

It is an arithmetic number, because the mean of its divisors is an integer number (1926720).

Almost surely, 2^21655497 is an apocalyptic number.

It is an amenable number.

21655497 is a deficient number, since it is larger than the sum of its proper divisors (9172023).

21655497 is a wasteful number, since it uses less digits than its factorization.

21655497 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5444.

The product of its digits is 75600, while the sum is 39.

The square root of 21655497 is about 4653.5467119177. The cubic root of 21655497 is about 278.7336392363.

The spelling of 21655497 in words is "twenty-one million, six hundred fifty-five thousand, four hundred ninety-seven".