21213543315997 has 2 divisors, whose sum is σ = 21213543315998. Its totient is φ = 21213543315996.

The previous prime is 21213543315989. The next prime is 21213543316027. The reversal of 21213543315997 is 79951334531212.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 10868224296601 + 10345319019396 = 3296699^2 + 3216414^2 .

It is a cyclic number.

It is not a de Polignac number, because 21213543315997 - 2³ = 21213543315989 is a prime.

It is a super-2 number, since 2×21213543315997² (a number of 27 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21213543315977) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10606771657998 + 10606771657999.

It is an arithmetic number, because the mean of its divisors is an integer number (10606771657999).

Almost surely, 2^{21213543315997} is an apocalyptic number.

It is an amenable number.

21213543315997 is a deficient number, since it is larger than the sum of its proper divisors (1).

21213543315997 is an equidigital number, since it uses as much as digits as its factorization.

21213543315997 is an evil number, because the sum of its binary digits is even.

The product of its digits is 6123600, while the sum is 55.

The spelling of 21213543315997 in words is "twenty-one trillion, two hundred thirteen billion, five hundred forty-three million, three hundred fifteen thousand, nine hundred ninety-seven".