21913261 has 4 divisors (see below), whose sum is σ = 21922812. Its totient is φ = 21903712.

The previous prime is 21913237. The next prime is 21913277. The reversal of 21913261 is 16231912.

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 8590761 + 13322500 = 2931^2 + 3650^2 .

It is a cyclic number.

It is not a de Polignac number, because 21913261 - 2¹¹ = 21911213 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 (21913201) 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, 975 + ... + 6691.

It is an arithmetic number, because the mean of its divisors is an integer number (5480703).

Almost surely, 2^21913261 is an apocalyptic number.

It is an amenable number.

21913261 is a deficient number, since it is larger than the sum of its proper divisors (9551).

21913261 is an equidigital number, since it uses as much as digits as its factorization.

21913261 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9550.

The product of its digits is 648, while the sum is 25.

The square root of 21913261 is about 4681.1602194328. The cubic root of 21913261 is about 279.8351963856.

The spelling of 21913261 in words is "twenty-one million, nine hundred thirteen thousand, two hundred sixty-one".