21506266872 has 192 divisors, whose sum is σ = 61525526400. Its totient is φ = 6779013120.

The previous prime is 21506266871. The next prime is 21506266883. The reversal of 21506266872 is 27866260512.

21506266872 is a `hidden beast` number, since 2 + 1 + 506 + 2 + 66 + 87 + 2 = 666.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21506266871) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 14462113 + ... + 14463599.

It is an arithmetic number, because the mean of its divisors is an integer number (320445450).

Almost surely, 2^21506266872 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 21506266872, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (30762763200).

21506266872 is an abundant number, since it is smaller than the sum of its proper divisors (40019259528).

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

21506266872 is a wasteful number, since it uses less digits than its factorization.

21506266872 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1686 (or 1679 counting only the distinct ones).

The product of its (nonzero) digits is 483840, while the sum is 45.

The spelling of 21506266872 in words is "twenty-one billion, five hundred six million, two hundred sixty-six thousand, eight hundred seventy-two".