21991201437816 has 192 divisors, whose sum is σ = 65765659115520. Its totient is φ = 6595433994240.

The previous prime is 21991201437797. The next prime is 21991201437817. The reversal of 21991201437816 is 61873410219912.

21991201437816 is a `hidden beast` number, since 2 + 1 + 9 + 9 + 120 + 1 + 437 + 81 + 6 = 666.

It is a super-2 number, since 2×21991201437816² (a number of 27 digits) contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21991201437817) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 41682825 + ... + 42207111.

It is an arithmetic number, because the mean of its divisors is an integer number (342529474560).

Almost surely, 2^{21991201437816} is an apocalyptic number.

21991201437816 is a gapful number since it is divisible by the number (26) 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 21991201437816, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (32882829557760).

21991201437816 is an abundant number, since it is smaller than the sum of its proper divisors (43774457677704).

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

21991201437816 is a wasteful number, since it uses less digits than its factorization.

21991201437816 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 525446 (or 525439 counting only the distinct ones).

The product of its (nonzero) digits is 1306368, while the sum is 54.

The spelling of 21991201437816 in words is "twenty-one trillion, nine hundred ninety-one billion, two hundred one million, four hundred thirty-seven thousand, eight hundred sixteen".