21231220291 has 2 divisors, whose sum is σ = 21231220292. Its totient is φ = 21231220290.

The previous prime is 21231220289. The next prime is 21231220343. The reversal of 21231220291 is 19202213212.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21231220291 - 2¹ = 21231220289 is a prime.

Together with 21231220289, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (21231220091) 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 as a sum of consecutive naturals, namely, 10615610145 + 10615610146.

It is an arithmetic number, because the mean of its divisors is an integer number (10615610146).

Almost surely, 2^21231220291 is an apocalyptic number.

21231220291 is a deficient number, since it is larger than the sum of its proper divisors (1).

21231220291 is an equidigital number, since it uses as much as digits as its factorization.

21231220291 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 864, while the sum is 25.

The spelling of 21231220291 in words is "twenty-one billion, two hundred thirty-one million, two hundred twenty thousand, two hundred ninety-one".