21995261 has 4 divisors (see below), whose sum is σ = 22005852. Its totient is φ = 21984672.

The previous prime is 21995243. The next prime is 21995287. The reversal of 21995261 is 16259912.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in 2 ways, for example, as 12292036 + 9703225 = 3506^2 + 3115^2 .

It is a cyclic number.

It is not a de Polignac number, because 21995261 - 2¹⁰ = 21994237 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 (21925261) 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, 1040 + ... + 6713.

It is an arithmetic number, because the mean of its divisors is an integer number (5501463).

Almost surely, 2^21995261 is an apocalyptic number.

It is an amenable number.

21995261 is a deficient number, since it is larger than the sum of its proper divisors (10591).

21995261 is an equidigital number, since it uses as much as digits as its factorization.

21995261 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10590.

The product of its digits is 9720, while the sum is 35.

The square root of 21995261 is about 4689.9105535181. The cubic root of 21995261 is about 280.1838121292.

The spelling of 21995261 in words is "twenty-one million, nine hundred ninety-five thousand, two hundred sixty-one".