216425981 has 2 divisors, whose sum is σ = 216425982. Its totient is φ = 216425980.

The previous prime is 216425971. The next prime is 216426047. The reversal of 216425981 is 189524612.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 118613881 + 97812100 = 10891^2 + 9890^2 .

It is a cyclic number.

It is not a de Polignac number, because 216425981 - 2²⁶ = 149317117 is a prime.

It is a super-2 number, since 2×216425981² = 93680410503624722, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (216425971) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 108212990 + 108212991.

It is an arithmetic number, because the mean of its divisors is an integer number (108212991).

Almost surely, 2^216425981 is an apocalyptic number.

It is an amenable number.

216425981 is a deficient number, since it is larger than the sum of its proper divisors (1).

216425981 is an equidigital number, since it uses as much as digits as its factorization.

216425981 is an evil number, because the sum of its binary digits is even.

The product of its digits is 34560, while the sum is 38.

The square root of 216425981 is about 14711.4234865291. The cubic root of 216425981 is about 600.3941678480.

The spelling of 216425981 in words is "two hundred sixteen million, four hundred twenty-five thousand, nine hundred eighty-one".