213691661 has 2 divisors, whose sum is σ = 213691662. Its totient is φ = 213691660.

The previous prime is 213691637. The next prime is 213691669. The reversal of 213691661 is 166196312.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 204661636 + 9030025 = 14306^2 + 3005^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-213691661 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 (213691669) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 106845830 + 106845831.

It is an arithmetic number, because the mean of its divisors is an integer number (106845831).

Almost surely, 2^213691661 is an apocalyptic number.

It is an amenable number.

213691661 is a deficient number, since it is larger than the sum of its proper divisors (1).

213691661 is an equidigital number, since it uses as much as digits as its factorization.

213691661 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 11664, while the sum is 35.

The square root of 213691661 is about 14618.1962293574. The cubic root of 213691661 is about 597.8549897642.

The spelling of 213691661 in words is "two hundred thirteen million, six hundred ninety-one thousand, six hundred sixty-one".