21900999 has 4 divisors (see below), whose sum is σ = 29201336. Its totient is φ = 14600664.

The previous prime is 21900997. The next prime is 21901001. The reversal of 21900999 is 99900912.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is an interprime number because it is at equal distance from previous prime (21900997) and next prime (21901001).

It is not a de Polignac number, because 21900999 - 2¹ = 21900997 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21900997) 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, 3650164 + ... + 3650169.

It is an arithmetic number, because the mean of its divisors is an integer number (7300334).

Almost surely, 2^21900999 is an apocalyptic number.

21900999 is a deficient number, since it is larger than the sum of its proper divisors (7300337).

21900999 is an equidigital number, since it uses as much as digits as its factorization.

21900999 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7300336.

The product of its (nonzero) digits is 13122, while the sum is 39.

The square root of 21900999 is about 4679.8503181192. The cubic root of 21900999 is about 279.7829908679.

The spelling of 21900999 in words is "twenty-one million, nine hundred thousand, nine hundred ninety-nine".