21251513440 has 24 divisors (see below), whose sum is σ = 50206700880. Its totient is φ = 8500605312.

The previous prime is 21251513431. The next prime is 21251513441. The reversal of 21251513440 is 4431515212.

It is a junction number, because it is equal to n+sod(n) for n = 21251513399 and 21251513408.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21251513441) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 66410820 + ... + 66411139.

It is an arithmetic number, because the mean of its divisors is an integer number (2091945870).

Almost surely, 2^21251513440 is an apocalyptic number.

21251513440 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21251513440 is an abundant number, since it is smaller than the sum of its proper divisors (28955187440).

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

21251513440 is a wasteful number, since it uses less digits than its factorization.

21251513440 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 132821974 (or 132821966 counting only the distinct ones).

The product of its (nonzero) digits is 4800, while the sum is 28.

The spelling of 21251513440 in words is "twenty-one billion, two hundred fifty-one million, five hundred thirteen thousand, four hundred forty".