21610261 has 4 divisors (see below), whose sum is σ = 21707392. Its totient is φ = 21513132.

The previous prime is 21610241. The next prime is 21610279. The reversal of 21610261 is 16201612.

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 a de Polignac number, because none of the positive numbers 2^k-21610261 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 (21610241) 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, 48231 + ... + 48676.

It is an arithmetic number, because the mean of its divisors is an integer number (5426848).

Almost surely, 2^21610261 is an apocalyptic number.

It is an amenable number.

21610261 is a deficient number, since it is larger than the sum of its proper divisors (97131).

21610261 is an equidigital number, since it uses as much as digits as its factorization.

21610261 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 97130.

The product of its (nonzero) digits is 144, while the sum is 19.

The square root of 21610261 is about 4648.6837922147. The cubic root of 21610261 is about 278.5394224272.

Adding to 21610261 its reverse (16201612), we get a palindrome (37811873).

The spelling of 21610261 in words is "twenty-one million, six hundred ten thousand, two hundred sixty-one".