21897021 has 8 divisors (see below), whose sum is σ = 29229984. Its totient is φ = 14581040.

The previous prime is 21897017. The next prime is 21897053. The reversal of 21897021 is 12079812.

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

It is a cyclic number.

It is not a de Polignac number, because 21897021 - 2² = 21897017 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21897021.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21897011) 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, 846 + ... + 6671.

It is an arithmetic number, because the mean of its divisors is an integer number (3653748).

Almost surely, 2^21897021 is an apocalyptic number.

It is an amenable number.

21897021 is a deficient number, since it is larger than the sum of its proper divisors (7332963).

21897021 is an equidigital number, since it uses as much as digits as its factorization.

21897021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8491.

The product of its (nonzero) digits is 2016, while the sum is 30.

The square root of 21897021 is about 4679.4252852247. The cubic root of 21897021 is about 279.7660503297.

The spelling of 21897021 in words is "twenty-one million, eight hundred ninety-seven thousand, twenty-one".