212399981 has 2 divisors, whose sum is σ = 212399982. Its totient is φ = 212399980.

The previous prime is 212399951. The next prime is 212400037. The reversal of 212399981 is 189993212.

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., 146627881 + 65772100 = 12109^2 + 8110^2 .

It is a cyclic number.

It is not a de Polignac number, because 212399981 - 2²⁶ = 145291117 is a prime.

It is a super-2 number, since 2×212399981² = 90227503857600722, which contains 22 as substring.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (212399951) 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, 106199990 + 106199991.

It is an arithmetic number, because the mean of its divisors is an integer number (106199991).

Almost surely, 2^212399981 is an apocalyptic number.

It is an amenable number.

212399981 is a deficient number, since it is larger than the sum of its proper divisors (1).

212399981 is an equidigital number, since it uses as much as digits as its factorization.

212399981 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 69984, while the sum is 44.

The square root of 212399981 is about 14573.9487099413. The cubic root of 212399981 is about 596.6479569608.

The spelling of 212399981 in words is "two hundred twelve million, three hundred ninety-nine thousand, nine hundred eighty-one".