21131220361 has 2 divisors, whose sum is σ = 21131220362. Its totient is φ = 21131220360.

The previous prime is 21131220311. The next prime is 21131220413. The reversal of 21131220361 is 16302213112.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 17541413136 + 3589807225 = 132444^2 + 59915^2 .

It is a cyclic number.

It is not a de Polignac number, because 21131220361 - 2⁷ = 21131220233 is a prime.

It is not a weakly prime, because it can be changed into another prime (21131220311) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10565610180 + 10565610181.

It is an arithmetic number, because the mean of its divisors is an integer number (10565610181).

Almost surely, 2^21131220361 is an apocalyptic number.

It is an amenable number.

21131220361 is a deficient number, since it is larger than the sum of its proper divisors (1).

21131220361 is an equidigital number, since it uses as much as digits as its factorization.

21131220361 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 432, while the sum is 22.

Adding to 21131220361 its reverse (16302213112), we get a palindrome (37433433473).

The spelling of 21131220361 in words is "twenty-one billion, one hundred thirty-one million, two hundred twenty thousand, three hundred sixty-one".