21178909512 has 256 divisors, whose sum is σ = 64350720000. Its totient is φ = 6431374080.

The previous prime is 21178909511. The next prime is 21178909517. The reversal of 21178909512 is 21590987112.

It is not an unprimeable number, because it can be changed into a prime (21178909511) by changing a digit.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 11379462 + ... + 11381322.

It is an arithmetic number, because the mean of its divisors is an integer number (251370000).

Almost surely, 2^21178909512 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 21178909512, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (32175360000).

21178909512 is an abundant number, since it is smaller than the sum of its proper divisors (43171810488).

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

21178909512 is a wasteful number, since it uses less digits than its factorization.

21178909512 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2001 (or 1991 counting only the distinct ones).

The product of its (nonzero) digits is 90720, while the sum is 45.

The spelling of 21178909512 in words is "twenty-one billion, one hundred seventy-eight million, nine hundred nine thousand, five hundred twelve".