21903891 has 8 divisors (see below), whose sum is σ = 29237184. Its totient is φ = 14586600.

The previous prime is 21903857. The next prime is 21903901. The reversal of 21903891 is 19830912.

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

It is not a de Polignac number, because 21903891 - 2⁹ = 21903379 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21903811) 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, 321 + ... + 6626.

It is an arithmetic number, because the mean of its divisors is an integer number (3654648).

Almost surely, 2^21903891 is an apocalyptic number.

21903891 is a deficient number, since it is larger than the sum of its proper divisors (7333293).

21903891 is a wasteful number, since it uses less digits than its factorization.

21903891 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8001.

The product of its (nonzero) digits is 3888, while the sum is 33.

The square root of 21903891 is about 4680.1592921609. The cubic root of 21903891 is about 279.7953053259.

The spelling of 21903891 in words is "twenty-one million, nine hundred three thousand, eight hundred ninety-one".