21137261 has 4 divisors (see below), whose sum is σ = 21181152. Its totient is φ = 21093372.

The previous prime is 21137251. The next prime is 21137267. The reversal of 21137261 is 16273112.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21137261 - 2¹⁰ = 21136237 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 (21137267) 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, 21215 + ... + 22188.

It is an arithmetic number, because the mean of its divisors is an integer number (5295288).

Almost surely, 2^21137261 is an apocalyptic number.

It is an amenable number.

21137261 is a deficient number, since it is larger than the sum of its proper divisors (43891).

21137261 is an equidigital number, since it uses as much as digits as its factorization.

21137261 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 43890.

The product of its digits is 504, while the sum is 23.

The square root of 21137261 is about 4597.5277051911. The cubic root of 21137261 is about 276.4922122401.

The spelling of 21137261 in words is "twenty-one million, one hundred thirty-seven thousand, two hundred sixty-one".