21128091 has 8 divisors (see below), whose sum is σ = 28233744. Its totient is φ = 14053920.

The previous prime is 21128087. The next prime is 21128117. The reversal of 21128091 is 19082112.

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

It is not a de Polignac number, because 21128091 - 2² = 21128087 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21121091) 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, 6256 + ... + 9021.

It is an arithmetic number, because the mean of its divisors is an integer number (3529218).

Almost surely, 2^21128091 is an apocalyptic number.

21128091 is a deficient number, since it is larger than the sum of its proper divisors (7105653).

21128091 is a wasteful number, since it uses less digits than its factorization.

21128091 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 15741.

The product of its (nonzero) digits is 288, while the sum is 24.

The square root of 21128091 is about 4596.5303218841. The cubic root of 21128091 is about 276.4522228216.

The spelling of 21128091 in words is "twenty-one million, one hundred twenty-eight thousand, ninety-one".