21276591 has 32 divisors (see below), whose sum is σ = 33707520. Its totient is φ = 11684736.

The previous prime is 21276583. The next prime is 21276611. The reversal of 21276591 is 19567212.

It is not a de Polignac number, because 21276591 - 2³ = 21276583 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21276551) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 107905 + ... + 108101.

It is an arithmetic number, because the mean of its divisors is an integer number (1053360).

Almost surely, 2^21276591 is an apocalyptic number.

21276591 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

21276591 is a deficient number, since it is larger than the sum of its proper divisors (12430929).

21276591 is a wasteful number, since it uses less digits than its factorization.

21276591 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 383.

The product of its digits is 7560, while the sum is 33.

The square root of 21276591 is about 4612.6555258332. The cubic root of 21276591 is about 277.0983980553.

It can be divided in two parts, 21276 and 591, that multiplied together give a square (12574116 = 3546²).

The spelling of 21276591 in words is "twenty-one million, two hundred seventy-six thousand, five hundred ninety-one".