21360851820 has 672 divisors, whose sum is σ = 85671613440. Its totient is φ = 4342740480.

The previous prime is 21360851807. The next prime is 21360851843. The reversal of 21360851820 is 2815806312.

It is a happy number.

21360851820 is a `hidden beast` number, since 2 + 13 + 608 + 5 + 18 + 20 = 666.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is an unprimeable number.

It is a polite number, since it can be written in 223 ways as a sum of consecutive naturals, for example, 59500801 + ... + 59501159.

It is an arithmetic number, because the mean of its divisors is an integer number (127487520).

Almost surely, 2^21360851820 is an apocalyptic number.

21360851820 is a gapful number since it is divisible by the number (20) 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 21360851820, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (42835806720).

21360851820 is an abundant number, since it is smaller than the sum of its proper divisors (64310761620).

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

21360851820 is a wasteful number, since it uses less digits than its factorization.

21360851820 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 457 (or 440 counting only the distinct ones).

The product of its (nonzero) digits is 23040, while the sum is 36.

The spelling of 21360851820 in words is "twenty-one billion, three hundred sixty million, eight hundred fifty-one thousand, eight hundred twenty".