21990391613 has 2 divisors, whose sum is σ = 21990391614. Its totient is φ = 21990391612.

The previous prime is 21990391547. The next prime is 21990391637. The reversal of 21990391613 is 31619309912.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 21839519524 + 150872089 = 147782^2 + 12283^2 .

It is a cyclic number.

It is not a de Polignac number, because 21990391613 - 2¹⁰ = 21990390589 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21990393613) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10995195806 + 10995195807.

It is an arithmetic number, because the mean of its divisors is an integer number (10995195807).

Almost surely, 2^21990391613 is an apocalyptic number.

It is an amenable number.

21990391613 is a deficient number, since it is larger than the sum of its proper divisors (1).

21990391613 is an equidigital number, since it uses as much as digits as its factorization.

21990391613 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 78732, while the sum is 44.

The spelling of 21990391613 in words is "twenty-one billion, nine hundred ninety million, three hundred ninety-one thousand, six hundred thirteen".