21955613 has 2 divisors, whose sum is σ = 21955614. Its totient is φ = 21955612.

The previous prime is 21955589. The next prime is 21955631. The reversal of 21955613 is 31655912.

Together with next prime (21955631) it forms an Ormiston pair, because they use the same digits, order apart.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 21780889 + 174724 = 4667^2 + 418^2 .

It is a cyclic number.

It is not a de Polignac number, because 21955613 - 2¹⁰ = 21954589 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 21955613.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21955673) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10977806 + 10977807.

It is an arithmetic number, because the mean of its divisors is an integer number (10977807).

Almost surely, 2^21955613 is an apocalyptic number.

It is an amenable number.

21955613 is a deficient number, since it is larger than the sum of its proper divisors (1).

21955613 is an equidigital number, since it uses as much as digits as its factorization.

21955613 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 8100, while the sum is 32.

The square root of 21955613 is about 4685.6817006707. The cubic root of 21955613 is about 280.0153605519.

The spelling of 21955613 in words is "twenty-one million, nine hundred fifty-five thousand, six hundred thirteen".