21161397233 has 4 divisors (see below), whose sum is σ = 21165953700. Its totient is φ = 21156840768.

The previous prime is 21161397221. The next prime is 21161397259. The reversal of 21161397233 is 33279316112.

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 12560133184 + 8601264049 = 112072^2 + 92743^2 .

It is a cyclic number.

It is not a de Polignac number, because 21161397233 - 2²² = 21157202929 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21161397263) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2271260 + ... + 2280557.

It is an arithmetic number, because the mean of its divisors is an integer number (5291488425).

Almost surely, 2^21161397233 is an apocalyptic number.

It is an amenable number.

21161397233 is a deficient number, since it is larger than the sum of its proper divisors (4556467).

21161397233 is an equidigital number, since it uses as much as digits as its factorization.

21161397233 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4556466.

The product of its digits is 40824, while the sum is 38.

The spelling of 21161397233 in words is "twenty-one billion, one hundred sixty-one million, three hundred ninety-seven thousand, two hundred thirty-three".