21491155 has 12 divisors (see below), whose sum is σ = 30000240. Its totient is φ = 14736624.

The previous prime is 21491149. The next prime is 21491189. The reversal of 21491155 is 55119412.

It is not a de Polignac number, because 21491155 - 2⁷ = 21491027 is a prime.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 43615 + ... + 44104.

It is an arithmetic number, because the mean of its divisors is an integer number (2500020).

Almost surely, 2^21491155 is an apocalyptic number.

21491155 is a deficient number, since it is larger than the sum of its proper divisors (8509085).

21491155 is an equidigital number, since it uses as much as digits as its factorization.

21491155 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 87738 (or 87731 counting only the distinct ones).

The product of its digits is 1800, while the sum is 28.

The square root of 21491155 is about 4635.8553687534. The cubic root of 21491155 is about 278.0267515619.

The spelling of 21491155 in words is "twenty-one million, four hundred ninety-one thousand, one hundred fifty-five".