21451621 has 2 divisors, whose sum is σ = 21451622. Its totient is φ = 21451620.

The previous prime is 21451613. The next prime is 21451631. The reversal of 21451621 is 12615412.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20349121 + 1102500 = 4511^2 + 1050^2 .

It is a cyclic number.

It is not a de Polignac number, because 21451621 - 2³ = 21451613 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21451592 and 21451601.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21451631) 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, 10725810 + 10725811.

It is an arithmetic number, because the mean of its divisors is an integer number (10725811).

Almost surely, 2^21451621 is an apocalyptic number.

It is an amenable number.

21451621 is a deficient number, since it is larger than the sum of its proper divisors (1).

21451621 is an equidigital number, since it uses as much as digits as its factorization.

21451621 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 480, while the sum is 22.

The square root of 21451621 is about 4631.5894679904. The cubic root of 21451621 is about 277.8561657823.

The spelling of 21451621 in words is "twenty-one million, four hundred fifty-one thousand, six hundred twenty-one".