21137491 has 8 divisors (see below), whose sum is σ = 21924000. Its totient is φ = 20354880.

The previous prime is 21137489. The next prime is 21137497. The reversal of 21137491 is 19473112.

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 21137491 - 2¹ = 21137489 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21137497) 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, 14410 + ... + 15808.

It is an arithmetic number, because the mean of its divisors is an integer number (2740500).

Almost surely, 2^21137491 is an apocalyptic number.

21137491 is a deficient number, since it is larger than the sum of its proper divisors (786509).

21137491 is a wasteful number, since it uses less digits than its factorization.

21137491 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1949.

The product of its digits is 1512, while the sum is 28.

The square root of 21137491 is about 4597.5527185667. The cubic root of 21137491 is about 276.4932150975.

It can be divided in two parts, 2113 and 7491, that added together give a square (9604 = 98²).

The spelling of 21137491 in words is "twenty-one million, one hundred thirty-seven thousand, four hundred ninety-one".