21506156065 has 16 divisors (see below), whose sum is σ = 25926645888. Its totient is φ = 17125593856.

The previous prime is 21506156047. The next prime is 21506156071. The reversal of 21506156065 is 56065160512.

It is a cyclic number.

It is not a de Polignac number, because 21506156065 - 2⁹ = 21506155553 is a prime.

It is a Duffinian 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, 1018404 + ... + 1039306.

It is an arithmetic number, because the mean of its divisors is an integer number (1620415368).

Almost surely, 2^21506156065 is an apocalyptic number.

It is an amenable number.

21506156065 is a deficient number, since it is larger than the sum of its proper divisors (4420489823).

21506156065 is a wasteful number, since it uses less digits than its factorization.

21506156065 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 21848.

The product of its (nonzero) digits is 54000, while the sum is 37.

The spelling of 21506156065 in words is "twenty-one billion, five hundred six million, one hundred fifty-six thousand, sixty-five".