21015778611 has 8 divisors (see below), whose sum is σ = 28143401680. Its totient is φ = 13949337312.

The previous prime is 21015778603. The next prime is 21015778631. The reversal of 21015778611 is 11687751012.

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

It is not a de Polignac number, because 21015778611 - 2³ = 21015778603 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21015778611.

It is not an unprimeable number, because it can be changed into a prime (21015778601) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 15294640 + ... + 15296013.

It is an arithmetic number, because the mean of its divisors is an integer number (3517925210).

Almost surely, 2^21015778611 is an apocalyptic number.

21015778611 is a deficient number, since it is larger than the sum of its proper divisors (7127623069).

21015778611 is a wasteful number, since it uses less digits than its factorization.

21015778611 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 30590885.

The product of its (nonzero) digits is 23520, while the sum is 39.

The spelling of 21015778611 in words is "twenty-one billion, fifteen million, seven hundred seventy-eight thousand, six hundred eleven".