21802997 has 4 divisors (see below), whose sum is σ = 21854016. Its totient is φ = 21751980.

The previous prime is 21802987. The next prime is 21802999. The reversal of 21802997 is 79920812.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21802997 - 2⁸ = 21802741 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 21802997.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21802999) 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, 24863 + ... + 25724.

It is an arithmetic number, because the mean of its divisors is an integer number (5463504).

Almost surely, 2^21802997 is an apocalyptic number.

It is an amenable number.

21802997 is a deficient number, since it is larger than the sum of its proper divisors (51019).

21802997 is an equidigital number, since it uses as much as digits as its factorization.

21802997 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 51018.

The product of its (nonzero) digits is 18144, while the sum is 38.

The square root of 21802997 is about 4669.3679443796. The cubic root of 21802997 is about 279.3650450470.

The spelling of 21802997 in words is "twenty-one million, eight hundred two thousand, nine hundred ninety-seven".