20945621 has 2 divisors, whose sum is σ = 20945622. Its totient is φ = 20945620.

The previous prime is 20945609. The next prime is 20945623. The reversal of 20945621 is 12654902.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 13322500 + 7623121 = 3650^2 + 2761^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20945621 is a prime.

It is a Sophie Germain prime.

Together with 20945623, it forms a pair of twin primes.

It is a Chen prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20945623) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10472810 + 10472811.

It is an arithmetic number, because the mean of its divisors is an integer number (10472811).

Almost surely, 2^20945621 is an apocalyptic number.

It is an amenable number.

20945621 is a deficient number, since it is larger than the sum of its proper divisors (1).

20945621 is an equidigital number, since it uses as much as digits as its factorization.

20945621 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 4320, while the sum is 29.

The square root of 20945621 is about 4576.6386136552. The cubic root of 20945621 is about 275.6540728413.

The spelling of 20945621 in words is "twenty million, nine hundred forty-five thousand, six hundred twenty-one".