16921541621 has 2 divisors, whose sum is σ = 16921541622. Its totient is φ = 16921541620.

The previous prime is 16921541603. The next prime is 16921541627. The reversal of 16921541621 is 12614512961.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 11596920721 + 5324620900 = 107689^2 + 72970^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-16921541621 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (16921541627) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 8460770810 + 8460770811.

It is an arithmetic number, because the mean of its divisors is an integer number (8460770811).

Almost surely, 2^16921541621 is an apocalyptic number.

It is an amenable number.

16921541621 is a deficient number, since it is larger than the sum of its proper divisors (1).

16921541621 is an equidigital number, since it uses as much as digits as its factorization.

16921541621 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 25920, while the sum is 38.

The spelling of 16921541621 in words is "sixteen billion, nine hundred twenty-one million, five hundred forty-one thousand, six hundred twenty-one".