213031991 has 2 divisors, whose sum is σ = 213031992. Its totient is φ = 213031990.

The previous prime is 213031961. The next prime is 213032089. The reversal of 213031991 is 199130312.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 213031991 - 2¹⁰ = 213030967 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (213031961) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 106515995 + 106515996.

It is an arithmetic number, because the mean of its divisors is an integer number (106515996).

Almost surely, 2^213031991 is an apocalyptic number.

213031991 is a deficient number, since it is larger than the sum of its proper divisors (1).

213031991 is an equidigital number, since it uses as much as digits as its factorization.

213031991 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1458, while the sum is 29.

The square root of 213031991 is about 14595.6154717778. The cubic root of 213031991 is about 597.2391592676.

The spelling of 213031991 in words is "two hundred thirteen million, thirty-one thousand, nine hundred ninety-one".