212221991 has 2 divisors, whose sum is σ = 212221992. Its totient is φ = 212221990.

The previous prime is 212221979. The next prime is 212222009. The reversal of 212221991 is 199122212.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 212221991 - 2⁶ = 212221927 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (212220991) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 106110995 + 106110996.

It is an arithmetic number, because the mean of its divisors is an integer number (106110996).

Almost surely, 2^212221991 is an apocalyptic number.

212221991 is a deficient number, since it is larger than the sum of its proper divisors (1).

212221991 is an equidigital number, since it uses as much as digits as its factorization.

212221991 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1296, while the sum is 29.

The square root of 212221991 is about 14567.8409862272. The cubic root of 212221991 is about 596.4812478311.

The spelling of 212221991 in words is "two hundred twelve million, two hundred twenty-one thousand, nine hundred ninety-one".