21892391 has 4 divisors (see below), whose sum is σ = 21901800. Its totient is φ = 21882984.

The previous prime is 21892373. The next prime is 21892399. The reversal of 21892391 is 19329812.

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 is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21892391 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 (21892399) 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, 1625 + ... + 6813.

It is an arithmetic number, because the mean of its divisors is an integer number (5475450).

Almost surely, 2^21892391 is an apocalyptic number.

21892391 is a deficient number, since it is larger than the sum of its proper divisors (9409).

21892391 is an equidigital number, since it uses as much as digits as its factorization.

21892391 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9408.

The product of its digits is 7776, while the sum is 35.

The square root of 21892391 is about 4678.9305401983. The cubic root of 21892391 is about 279.7463306287.

The spelling of 21892391 in words is "twenty-one million, eight hundred ninety-two thousand, three hundred ninety-one".