21206921917065 has 16 divisors (see below), whose sum is σ = 33936023616768. Its totient is φ = 11308708839296.

The previous prime is 21206921916911. The next prime is 21206921917117. The reversal of 21206921917065 is 56071912960212.

It is a cyclic number.

It is not a de Polignac number, because 21206921917065 - 2⁸ = 21206921916809 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21206921916999 and 21206921917017.

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, 102988497 + ... + 103194206.

It is an arithmetic number, because the mean of its divisors is an integer number (2121001476048).

Almost surely, 2^{21206921917065} is an apocalyptic number.

It is an amenable number.

21206921917065 is a deficient number, since it is larger than the sum of its proper divisors (12729101699703).

21206921917065 is a wasteful number, since it uses less digits than its factorization.

21206921917065 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 206189568.

The product of its (nonzero) digits is 816480, while the sum is 51.

The spelling of 21206921917065 in words is "twenty-one trillion, two hundred six billion, nine hundred twenty-one million, nine hundred seventeen thousand, sixty-five".