21935621 has 2 divisors, whose sum is σ = 21935622. Its totient is φ = 21935620.

The previous prime is 21935609. The next prime is 21935623. The reversal of 21935621 is 12653912.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 19936225 + 1999396 = 4465^2 + 1414^2 .

It is a cyclic number.

It is not a de Polignac number, because 21935621 - 2¹⁴ = 21919237 is a prime.

Together with 21935623, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21935623) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10967810 + 10967811.

It is an arithmetic number, because the mean of its divisors is an integer number (10967811).

Almost surely, 2^21935621 is an apocalyptic number.

It is an amenable number.

21935621 is a deficient number, since it is larger than the sum of its proper divisors (1).

21935621 is an equidigital number, since it uses as much as digits as its factorization.

21935621 is an evil number, because the sum of its binary digits is even.

The product of its digits is 3240, while the sum is 29.

The square root of 21935621 is about 4683.5479073028. The cubic root of 21935621 is about 279.9303440676.

The spelling of 21935621 in words is "twenty-one million, nine hundred thirty-five thousand, six hundred twenty-one".