21115491 has 4 divisors (see below), whose sum is σ = 28153992. Its totient is φ = 14076992.

The previous prime is 21115453. The next prime is 21115511. The reversal of 21115491 is 19451112.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21115491 - 2⁶ = 21115427 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21115421) 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, 3519246 + ... + 3519251.

It is an arithmetic number, because the mean of its divisors is an integer number (7038498).

Almost surely, 2^21115491 is an apocalyptic number.

21115491 is a deficient number, since it is larger than the sum of its proper divisors (7038501).

21115491 is an equidigital number, since it uses as much as digits as its factorization.

21115491 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7038500.

The product of its digits is 360, while the sum is 24.

The square root of 21115491 is about 4595.1595184498. The cubic root of 21115491 is about 276.3972566524.

The spelling of 21115491 in words is "twenty-one million, one hundred fifteen thousand, four hundred ninety-one".