21215513440 has 48 divisors (see below), whose sum is σ = 54678168720. Its totient is φ = 7714731520.

The previous prime is 21215513393. The next prime is 21215513453. The reversal of 21215513440 is 4431551212.

It is a junction number, because it is equal to n+sod(n) for n = 21215513399 and 21215513408.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 6025375 + ... + 6028894.

It is an arithmetic number, because the mean of its divisors is an integer number (1139128515).

Almost surely, 2^21215513440 is an apocalyptic number.

21215513440 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21215513440 is an abundant number, since it is smaller than the sum of its proper divisors (33462655280).

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

21215513440 is a wasteful number, since it uses less digits than its factorization.

21215513440 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12054295 (or 12054287 counting only the distinct ones).

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

The spelling of 21215513440 in words is "twenty-one billion, two hundred fifteen million, five hundred thirteen thousand, four hundred forty".