21890751 has 4 divisors (see below), whose sum is σ = 29187672. Its totient is φ = 14593832.

The previous prime is 21890723. The next prime is 21890773. The reversal of 21890751 is 15709812.

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

It is a cyclic number.

It is not a de Polignac number, because 21890751 - 2⁵ = 21890719 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21890651) 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, 3648456 + ... + 3648461.

It is an arithmetic number, because the mean of its divisors is an integer number (7296918).

Almost surely, 2^21890751 is an apocalyptic number.

21890751 is a deficient number, since it is larger than the sum of its proper divisors (7296921).

21890751 is an equidigital number, since it uses as much as digits as its factorization.

21890751 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7296920.

The product of its (nonzero) digits is 5040, while the sum is 33.

The square root of 21890751 is about 4678.7552831923. The cubic root of 21890751 is about 279.7393450138.

The spelling of 21890751 in words is "twenty-one million, eight hundred ninety thousand, seven hundred fifty-one".