21491255 has 8 divisors (see below), whose sum is σ = 26174832. Its totient is φ = 16936128.

The previous prime is 21491251. The next prime is 21491263. The reversal of 21491255 is 55219412.

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

It is a cyclic number.

It is not a de Polignac number, because 21491255 - 2² = 21491251 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21491251) 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, 31742 + ... + 32411.

It is an arithmetic number, because the mean of its divisors is an integer number (3271854).

Almost surely, 2^21491255 is an apocalyptic number.

21491255 is a deficient number, since it is larger than the sum of its proper divisors (4683577).

21491255 is an equidigital number, since it uses as much as digits as its factorization.

21491255 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 64225.

The product of its digits is 3600, while the sum is 29.

The square root of 21491255 is about 4635.8661542370. The cubic root of 21491255 is about 278.0271827879.

The spelling of 21491255 in words is "twenty-one million, four hundred ninety-one thousand, two hundred fifty-five".