21252581780 has 24 divisors (see below), whose sum is σ = 45362070600. Its totient is φ = 8361671040.

The previous prime is 21252581723. The next prime is 21252581783. The reversal of 21252581780 is 8718525212.

It can be written as a sum of positive squares in 4 ways, for example, as 1438078084 + 19814503696 = 37922^2 + 140764^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21252581783) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 8708855 + ... + 8711294.

It is an arithmetic number, because the mean of its divisors is an integer number (1890086275).

Almost surely, 2^21252581780 is an apocalyptic number.

21252581780 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21252581780 is an abundant number, since it is smaller than the sum of its proper divisors (24109488820).

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

21252581780 is a wasteful number, since it uses less digits than its factorization.

21252581780 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 17420219 (or 17420217 counting only the distinct ones).

The product of its (nonzero) digits is 89600, while the sum is 41.

The spelling of 21252581780 in words is "twenty-one billion, two hundred fifty-two million, five hundred eighty-one thousand, seven hundred eighty".