21812497 has 12 divisors (see below), whose sum is σ = 25538736. Its totient is φ = 18574920.

The previous prime is 21812471. The next prime is 21812501. The reversal of 21812497 is 79421812.

It is a de Polignac number, because none of the positive numbers 2^k-21812497 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21812447) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 6622 + ... + 9352.

It is an arithmetic number, because the mean of its divisors is an integer number (2128228).

Almost surely, 2^21812497 is an apocalyptic number.

It is an amenable number.

21812497 is a deficient number, since it is larger than the sum of its proper divisors (3726239).

21812497 is a wasteful number, since it uses less digits than its factorization.

21812497 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2908 (or 2901 counting only the distinct ones).

The product of its digits is 8064, while the sum is 34.

The square root of 21812497 is about 4670.3851018947. The cubic root of 21812497 is about 279.4056141265.

The spelling of 21812497 in words is "twenty-one million, eight hundred twelve thousand, four hundred ninety-seven".