21509452518 has 32 divisors (see below), whose sum is σ = 44058132096. Its totient is φ = 6996907008.

The previous prime is 21509452421. The next prime is 21509452537. The reversal of 21509452518 is 81525490512.

It is a self number, because there is not a number n which added to its sum of digits gives 21509452518.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 261321 + ... + 333627.

It is an arithmetic number, because the mean of its divisors is an integer number (1376816628).

Almost surely, 2^21509452518 is an apocalyptic number.

21509452518 is an abundant number, since it is smaller than the sum of its proper divisors (22548679578).

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

21509452518 is a wasteful number, since it uses less digits than its factorization.

21509452518 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 73508.

The product of its (nonzero) digits is 144000, while the sum is 42.

The spelling of 21509452518 in words is "twenty-one billion, five hundred nine million, four hundred fifty-two thousand, five hundred eighteen".