21619621 has 2 divisors, whose sum is σ = 21619622. Its totient is φ = 21619620.

The previous prime is 21619579. The next prime is 21619649. The reversal of 21619621 is 12691612.

It is an a-pointer prime, because the next prime (21619649) can be obtained adding 21619621 to its sum of digits (28).

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 21288996 + 330625 = 4614^2 + 575^2 .

It is a cyclic number.

It is not a de Polignac number, because 21619621 - 2⁹ = 21619109 is a prime.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21619621.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21619021) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10809810 + 10809811.

It is an arithmetic number, because the mean of its divisors is an integer number (10809811).

Almost surely, 2^21619621 is an apocalyptic number.

21619621 is the 2685-th hex number.

It is an amenable number.

21619621 is a deficient number, since it is larger than the sum of its proper divisors (1).

21619621 is an equidigital number, since it uses as much as digits as its factorization.

21619621 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1296, while the sum is 28.

The square root of 21619621 is about 4649.6904198022. The cubic root of 21619621 is about 278.5796309911.

The spelling of 21619621 in words is "twenty-one million, six hundred nineteen thousand, six hundred twenty-one".