21195991872 has 336 divisors, whose sum is σ = 71734021632. Its totient is φ = 6142625280.

The previous prime is 21195991793. The next prime is 21195991889. The reversal of 21195991872 is 27819959112.

It is a happy number.

21195991872 is a `hidden beast` number, since 21 + 19 + 599 + 18 + 7 + 2 = 666.

It is a Harshad number since it is a multiple of its sum of digits (54).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 3931963 + ... + 3937349.

It is an arithmetic number, because the mean of its divisors is an integer number (213494112).

Almost surely, 2^21195991872 is an apocalyptic number.

21195991872 is a gapful number since it is divisible by the number (22) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21195991872, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (35867010816).

21195991872 is an abundant number, since it is smaller than the sum of its proper divisors (50538029760).

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

21195991872 is a wasteful number, since it uses less digits than its factorization.

21195991872 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5448 (or 5426 counting only the distinct ones).

The product of its digits is 816480, while the sum is 54.

The spelling of 21195991872 in words is "twenty-one billion, one hundred ninety-five million, nine hundred ninety-one thousand, eight hundred seventy-two".