21137257 has 8 divisors (see below), whose sum is σ = 21900032. Its totient is φ = 20379600.

The previous prime is 21137251. The next prime is 21137267. The reversal of 21137257 is 75273112.

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 21137257 - 2²³ = 12748649 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21137251) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 8407 + ... + 10627.

It is an arithmetic number, because the mean of its divisors is an integer number (2737504).

Almost surely, 2^21137257 is an apocalyptic number.

It is an amenable number.

21137257 is a deficient number, since it is larger than the sum of its proper divisors (762775).

21137257 is a wasteful number, since it uses less digits than its factorization.

21137257 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2559.

The product of its digits is 2940, while the sum is 28.

The square root of 21137257 is about 4597.5272701747. The cubic root of 21137257 is about 276.4921947990.

The spelling of 21137257 in words is "twenty-one million, one hundred thirty-seven thousand, two hundred fifty-seven".