21812897 has 4 divisors (see below), whose sum is σ = 21823620. Its totient is φ = 21802176.

The previous prime is 21812891. The next prime is 21812899. The reversal of 21812897 is 79821812.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in 2 ways, for example, as 12103441 + 9709456 = 3479^2 + 3116^2 .

It is a cyclic number.

It is not a de Polignac number, because 21812897 - 2⁴ = 21812881 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21812897.

It is not an unprimeable number, because it can be changed into a prime (21812891) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1268 + ... + 6725.

It is an arithmetic number, because the mean of its divisors is an integer number (5455905).

Almost surely, 2^21812897 is an apocalyptic number.

It is an amenable number.

21812897 is a deficient number, since it is larger than the sum of its proper divisors (10723).

21812897 is an equidigital number, since it uses as much as digits as its factorization.

21812897 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10722.

The product of its digits is 16128, while the sum is 38.

The square root of 21812897 is about 4670.4279247195. The cubic root of 21812897 is about 279.4073220398.

The spelling of 21812897 in words is "twenty-one million, eight hundred twelve thousand, eight hundred ninety-seven".