20991628584 has 24 divisors (see below), whose sum is σ = 56852327610. Its totient is φ = 6997209504.

The previous prime is 20991628571. The next prime is 20991628589. The reversal of 20991628584 is 48582619902.

It is a happy number.

20991628584 is a `hidden beast` number, since 2 + 0 + 9 + 9 + 1 + 628 + 5 + 8 + 4 = 666.

It can be written as a sum of positive squares in only one way, i.e., 19649871684 + 1341756900 = 140178^2 + 36630^2 .

It is a tau number, because it is divible by the number of its divisors (24).

It is a self number, because there is not a number n which added to its sum of digits gives 20991628584.

It is not an unprimeable number, because it can be changed into a prime (20991628589) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 145775127 + ... + 145775270.

Almost surely, 2^20991628584 is an apocalyptic number.

20991628584 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

20991628584 is an abundant number, since it is smaller than the sum of its proper divisors (35860699026).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

20991628584 is a wasteful number, since it uses less digits than its factorization.

20991628584 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 291550409 (or 291550402 counting only the distinct ones).

The product of its (nonzero) digits is 2488320, while the sum is 54.

The spelling of 20991628584 in words is "twenty billion, nine hundred ninety-one million, six hundred twenty-eight thousand, five hundred eighty-four".