21521451540 has 48 divisors (see below), whose sum is σ = 60266828160. Its totient is φ = 5738409600.

The previous prime is 21521451517. The next prime is 21521451571. The reversal of 21521451540 is 4515412512.

It is a Harshad number since it is a multiple of its sum of digits (30).

It is a junction number, because it is equal to n+sod(n) for n = 21521451498 and 21521451507.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 785065 + ... + 812015.

It is an arithmetic number, because the mean of its divisors is an integer number (1255558920).

Almost surely, 2^21521451540 is an apocalyptic number.

21521451540 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21521451540 is an abundant number, since it is smaller than the sum of its proper divisors (38745376620).

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

21521451540 is a wasteful number, since it uses less digits than its factorization.

21521451540 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 40272 (or 40270 counting only the distinct ones).

The product of its (nonzero) digits is 8000, while the sum is 30.

The spelling of 21521451540 in words is "twenty-one billion, five hundred twenty-one million, four hundred fifty-one thousand, five hundred forty".