216251982581 has 2 divisors, whose sum is σ = 216251982582. Its totient is φ = 216251982580.

The previous prime is 216251982497. The next prime is 216251982589. The reversal of 216251982581 is 185289152612.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 173168338225 + 43083644356 = 416135^2 + 207566^2 .

It is a cyclic number.

It is not a de Polignac number, because 216251982581 - 2²² = 216247788277 is a prime.

It is a super-2 number, since 2×216251982581² (a number of 23 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (216251982589) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 108125991290 + 108125991291.

It is an arithmetic number, because the mean of its divisors is an integer number (108125991291).

Almost surely, 2^216251982581 is an apocalyptic number.

It is an amenable number.

216251982581 is a deficient number, since it is larger than the sum of its proper divisors (1).

216251982581 is an equidigital number, since it uses as much as digits as its factorization.

216251982581 is an evil number, because the sum of its binary digits is even.

The product of its digits is 691200, while the sum is 50.

The spelling of 216251982581 in words is "two hundred sixteen billion, two hundred fifty-one million, nine hundred eighty-two thousand, five hundred eighty-one".