21356261 has 4 divisors (see below), whose sum is σ = 21552300. Its totient is φ = 21160224.

The previous prime is 21356219. The next prime is 21356287. The reversal of 21356261 is 16265312.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 9728161 + 11628100 = 3119^2 + 3410^2 .

It is a cyclic number.

It is not a de Polignac number, because 21356261 - 2²² = 17161957 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21356261.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21356201) 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, 97856 + ... + 98073.

It is an arithmetic number, because the mean of its divisors is an integer number (5388075).

Almost surely, 2^21356261 is an apocalyptic number.

It is an amenable number.

21356261 is a deficient number, since it is larger than the sum of its proper divisors (196039).

21356261 is a wasteful number, since it uses less digits than its factorization.

21356261 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 196038.

The product of its digits is 2160, while the sum is 26.

The square root of 21356261 is about 4621.2834797272. The cubic root of 21356261 is about 277.4438313934.

The spelling of 21356261 in words is "twenty-one million, three hundred fifty-six thousand, two hundred sixty-one".