21171516912 has 360 divisors, whose sum is σ = 76057048704. Its totient is φ = 5582483712.

The previous prime is 21171516907. The next prime is 21171516959. The reversal of 21171516912 is 21961517112.

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

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 71 ways as a sum of consecutive naturals, for example, 4597203 + ... + 4601805.

Almost surely, 2^21171516912 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 21171516912, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (38028524352).

21171516912 is an abundant number, since it is smaller than the sum of its proper divisors (54885531792).

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

21171516912 is a wasteful number, since it uses less digits than its factorization.

21171516912 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4659 (or 4628 counting only the distinct ones).

The product of its digits is 7560, while the sum is 36.

The spelling of 21171516912 in words is "twenty-one billion, one hundred seventy-one million, five hundred sixteen thousand, nine hundred twelve".