21343561997 has 2 divisors, whose sum is σ = 21343561998. Its totient is φ = 21343561996.

The previous prime is 21343561991. The next prime is 21343562017. The reversal of 21343561997 is 79916534312.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 21287101801 + 56460196 = 145901^2 + 7514^2 .

It is a cyclic number.

It is not a de Polignac number, because 21343561997 - 2²⁴ = 21326784781 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21343561991) 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, 10671780998 + 10671780999.

It is an arithmetic number, because the mean of its divisors is an integer number (10671780999).

Almost surely, 2^21343561997 is an apocalyptic number.

It is an amenable number.

21343561997 is a deficient number, since it is larger than the sum of its proper divisors (1).

21343561997 is an equidigital number, since it uses as much as digits as its factorization.

21343561997 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1224720, while the sum is 50.

The spelling of 21343561997 in words is "twenty-one billion, three hundred forty-three million, five hundred sixty-one thousand, nine hundred ninety-seven".