21165358812 has 96 divisors (see below), whose sum is σ = 53851392000. Its totient is φ = 6431308032.

The previous prime is 21165358771. The next prime is 21165358873. The reversal of 21165358812 is 21885356112.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 4158133 + ... + 4163219.

It is an arithmetic number, because the mean of its divisors is an integer number (560952000).

Almost surely, 2^21165358812 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21165358812, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (26925696000).

21165358812 is an abundant number, since it is smaller than the sum of its proper divisors (32686033188).

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

21165358812 is a wasteful number, since it uses less digits than its factorization.

21165358812 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5435 (or 5433 counting only the distinct ones).

The product of its digits is 115200, while the sum is 42.

The spelling of 21165358812 in words is "twenty-one billion, one hundred sixty-five million, three hundred fifty-eight thousand, eight hundred twelve".