21990391717 has 32 divisors (see below), whose sum is σ = 26014348800. Its totient is φ = 18202060800.

The previous prime is 21990391699. The next prime is 21990391733. The reversal of 21990391717 is 71719309912.

It is not a de Polignac number, because 21990391717 - 2¹¹ = 21990389669 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21990391217) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 4819117 + ... + 4823677.

It is an arithmetic number, because the mean of its divisors is an integer number (812948400).

Almost surely, 2^21990391717 is an apocalyptic number.

It is an amenable number.

21990391717 is a deficient number, since it is larger than the sum of its proper divisors (4023957083).

21990391717 is a wasteful number, since it uses less digits than its factorization.

21990391717 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4837.

The product of its (nonzero) digits is 214326, while the sum is 49.

The spelling of 21990391717 in words is "twenty-one billion, nine hundred ninety million, three hundred ninety-one thousand, seven hundred seventeen".