21516783747 has 8 divisors (see below), whose sum is σ = 28690397520. Its totient is φ = 14343846240.

The previous prime is 21516783733. The next prime is 21516783787. The reversal of 21516783747 is 74738761512.

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

It is not a de Polignac number, because 21516783747 - 2⁷ = 21516783619 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21516783747.

It is not an unprimeable number, because it can be changed into a prime (21516783727) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 89472 + ... + 225917.

It is an arithmetic number, because the mean of its divisors is an integer number (3586299690).

Almost surely, 2^21516783747 is an apocalyptic number.

21516783747 is a deficient number, since it is larger than the sum of its proper divisors (7173613773).

21516783747 is a wasteful number, since it uses less digits than its factorization.

21516783747 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 338133.

The product of its digits is 1975680, while the sum is 51.

The spelling of 21516783747 in words is "twenty-one billion, five hundred sixteen million, seven hundred eighty-three thousand, seven hundred forty-seven".