21946991065 has 16 divisors (see below), whose sum is σ = 26997674256. Its totient is φ = 17117337600.

The previous prime is 21946991009. The next prime is 21946991089. The reversal of 21946991065 is 56019964912.

It is a happy number.

It can be written as a sum of positive squares in 8 ways, for example, as 1586269584 + 20360721481 = 39828^2 + 142691^2 .

It is not a de Polignac number, because 21946991065 - 2⁷ = 21946990937 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, 261025 + ... + 334705.

It is an arithmetic number, because the mean of its divisors is an integer number (1687354641).

Almost surely, 2^21946991065 is an apocalyptic number.

It is an amenable number.

21946991065 is a deficient number, since it is larger than the sum of its proper divisors (5050683191).

21946991065 is a wasteful number, since it uses less digits than its factorization.

21946991065 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 75180.

The product of its (nonzero) digits is 1049760, while the sum is 52.

The spelling of 21946991065 in words is "twenty-one billion, nine hundred forty-six million, nine hundred ninety-one thousand, sixty-five".