21156653620 has 48 divisors (see below), whose sum is σ = 46201881600. Its totient is φ = 8128023680.

The previous prime is 21156653593. The next prime is 21156653621. The reversal of 21156653620 is 2635665112.

It is a self number, because there is not a number n which added to its sum of digits gives 21156653620.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21156653621) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 15291 + ... + 206269.

It is an arithmetic number, because the mean of its divisors is an integer number (962539200).

Almost surely, 2^21156653620 is an apocalyptic number.

21156653620 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 21156653620, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (23100940800).

21156653620 is an abundant number, since it is smaller than the sum of its proper divisors (25045227980).

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

21156653620 is a wasteful number, since it uses less digits than its factorization.

21156653620 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 191208 (or 191206 counting only the distinct ones).

The product of its (nonzero) digits is 64800, while the sum is 37.

The spelling of 21156653620 in words is "twenty-one billion, one hundred fifty-six million, six hundred fifty-three thousand, six hundred twenty".