21050891 has 8 divisors (see below), whose sum is σ = 22318464. Its totient is φ = 19820160.

The previous prime is 21050873. The next prime is 21050921. The reversal of 21050891 is 19805012.

It is a happy number.

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

It is a de Polignac number, because none of the positive numbers 2^k-21050891 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 21050891.

It is not an unprimeable number, because it can be changed into a prime (21050801) 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, 8030 + ... + 10323.

It is an arithmetic number, because the mean of its divisors is an integer number (2789808).

Almost surely, 2^21050891 is an apocalyptic number.

21050891 is a deficient number, since it is larger than the sum of its proper divisors (1267573).

21050891 is a wasteful number, since it uses less digits than its factorization.

21050891 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 18421.

The product of its (nonzero) digits is 720, while the sum is 26.

The square root of 21050891 is about 4588.1249982972. The cubic root of 21050891 is about 276.1151019951.

The spelling of 21050891 in words is "twenty-one million, fifty thousand, eight hundred ninety-one".