21691851208824 has 16 divisors (see below), whose sum is σ = 54229628022120. Its totient is φ = 7230617069600.

The previous prime is 21691851208787. The next prime is 21691851208829. The reversal of 21691851208824 is 42880215819612.

It is a happy number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21691851208829) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 451913566827 + ... + 451913566874.

Almost surely, 2^{21691851208824} is an apocalyptic number.

21691851208824 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

21691851208824 is an abundant number, since it is smaller than the sum of its proper divisors (32537776813296).

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

21691851208824 is a wasteful number, since it uses less digits than its factorization.

21691851208824 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 903827133710 (or 903827133706 counting only the distinct ones).

The product of its (nonzero) digits is 4423680, while the sum is 57.

The spelling of 21691851208824 in words is "twenty-one trillion, six hundred ninety-one billion, eight hundred fifty-one million, two hundred eight thousand, eight hundred twenty-four".