21002787072 has 108 divisors (see below), whose sum is σ = 60776674140. Its totient is φ = 6975442944.

The previous prime is 21002786921. The next prime is 21002787077. The reversal of 21002787072 is 27078720012.

It can be written as a sum of positive squares in 2 ways, for example, as 10919414016 + 10083373056 = 104496^2 + 100416^2 .

It is a super-2 number, since 2×21002787072² (a number of 21 digits) contains 22 as substring.

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

It is not an unprimeable number, because it can be changed into a prime (21002787077) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 621754 + ... + 654662.

Almost surely, 2^21002787072 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 21002787072, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (30388337070).

21002787072 is an abundant number, since it is smaller than the sum of its proper divisors (39773887068).

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

21002787072 is a wasteful number, since it uses less digits than its factorization.

21002787072 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 33208 (or 33191 counting only the distinct ones).

The product of its (nonzero) digits is 21952, while the sum is 36.

The spelling of 21002787072 in words is "twenty-one billion, two million, seven hundred eighty-seven thousand, seventy-two".