21099599616 has 72 divisors (see below), whose sum is σ = 56215755904. Its totient is φ = 7025679360.

The previous prime is 21099599593. The next prime is 21099599663. The reversal of 21099599616 is 61699599012.

It is a Smith number, since the sum of its digits (57) coincides with the sum of the digits of its prime factors.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 728451 + ... + 756861.

Almost surely, 2^21099599616 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 21099599616, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28107877952).

21099599616 is an abundant number, since it is smaller than the sum of its proper divisors (35116156288).

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

21099599616 is an equidigital number, since it uses as much as digits as its factorization.

21099599616 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 29397 (or 29383 counting only the distinct ones).

The product of its (nonzero) digits is 2361960, while the sum is 57.

The spelling of 21099599616 in words is "twenty-one billion, ninety-nine million, five hundred ninety-nine thousand, six hundred sixteen".