21700621 has 2 divisors, whose sum is σ = 21700622. Its totient is φ = 21700620.

The previous prime is 21700597. The next prime is 21700631. The reversal of 21700621 is 12600712.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 14356521 + 7344100 = 3789^2 + 2710^2 .

It is a cyclic number.

It is not a de Polignac number, because 21700621 - 2⁷ = 21700493 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21700631) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10850310 + 10850311.

It is an arithmetic number, because the mean of its divisors is an integer number (10850311).

Almost surely, 2^21700621 is an apocalyptic number.

It is an amenable number.

21700621 is a deficient number, since it is larger than the sum of its proper divisors (1).

21700621 is an equidigital number, since it uses as much as digits as its factorization.

21700621 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 168, while the sum is 19.

The square root of 21700621 is about 4658.3925339112. The cubic root of 21700621 is about 278.9271059080.

Subtracting from 21700621 its reverse (12600712), we obtain a palindrome (9099909).

The spelling of 21700621 in words is "twenty-one million, seven hundred thousand, six hundred twenty-one".