21011665015 has 16 divisors (see below), whose sum is σ = 29124191520. Its totient is φ = 14382315520.

The previous prime is 21011664979. The next prime is 21011665067. The reversal of 21011665015 is 51056611012.

It is a happy number.

It is not a de Polignac number, because 21011665015 - 2⁹ = 21011664503 is a prime.

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, 11235250 + ... + 11237119.

It is an arithmetic number, because the mean of its divisors is an integer number (1820261970).

Almost surely, 2^21011665015 is an apocalyptic number.

21011665015 is a deficient number, since it is larger than the sum of its proper divisors (8112526505).

21011665015 is a wasteful number, since it uses less digits than its factorization.

21011665015 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 22472402.

The product of its (nonzero) digits is 1800, while the sum is 28.

The spelling of 21011665015 in words is "twenty-one billion, eleven million, six hundred sixty-five thousand, fifteen".