21144568538 has 8 divisors (see below), whose sum is σ = 31719065940. Its totient is φ = 10571546560.

The previous prime is 21144568517. The next prime is 21144568573. The reversal of 21144568538 is 83586544112.

It can be written as a sum of positive squares in 2 ways, for example, as 19163695489 + 1980873049 = 138433^2 + 44507^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a junction number, because it is equal to n+sod(n) for n = 21144568492 and 21144568501.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 332303 + ... + 390786.

Almost surely, 2^21144568538 is an apocalyptic number.

21144568538 is a deficient number, since it is larger than the sum of its proper divisors (10574497402).

21144568538 is a wasteful number, since it uses less digits than its factorization.

21144568538 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 737712.

The product of its digits is 921600, while the sum is 47.

The spelling of 21144568538 in words is "twenty-one billion, one hundred forty-four million, five hundred sixty-eight thousand, five hundred thirty-eight".