21956653261 has 4 divisors (see below), whose sum is σ = 22104013500. Its totient is φ = 21809293024.

The previous prime is 21956653237. The next prime is 21956653267. The reversal of 21956653261 is 16235665912.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 1078137225 + 20878516036 = 32835^2 + 144494^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21956653261 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21956653267) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 73679896 + ... + 73680193.

It is an arithmetic number, because the mean of its divisors is an integer number (5526003375).

Almost surely, 2^21956653261 is an apocalyptic number.

It is an amenable number.

21956653261 is a deficient number, since it is larger than the sum of its proper divisors (147360239).

21956653261 is a wasteful number, since it uses less digits than its factorization.

21956653261 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 147360238.

The product of its digits is 583200, while the sum is 46.

The spelling of 21956653261 in words is "twenty-one billion, nine hundred fifty-six million, six hundred fifty-three thousand, two hundred sixty-one".