21121279872 has 288 divisors, whose sum is σ = 71743248360. Its totient is φ = 5485455360.

The previous prime is 21121279849. The next prime is 21121279897. The reversal of 21121279872 is 27897212112.

It is a happy number.

It is a super-2 number, since 2×21121279872² (a number of 21 digits) contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (42).

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 2272098 + ... + 2281374.

Almost surely, 2^21121279872 is an apocalyptic number.

21121279872 is a gapful number since it is divisible by the number (22) 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 21121279872, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (35871624180).

21121279872 is an abundant number, since it is smaller than the sum of its proper divisors (50621968488).

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

21121279872 is a wasteful number, since it uses less digits than its factorization.

21121279872 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9330 (or 9300 counting only the distinct ones).

The product of its digits is 56448, while the sum is 42.

The spelling of 21121279872 in words is "twenty-one billion, one hundred twenty-one million, two hundred seventy-nine thousand, eight hundred seventy-two".