213931561 has 2 divisors, whose sum is σ = 213931562. Its totient is φ = 213931560.

The previous prime is 213931517. The next prime is 213931577. The reversal of 213931561 is 165139312.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 209351961 + 4579600 = 14469^2 + 2140^2 .

It is a cyclic number.

It is not a de Polignac number, because 213931561 - 2¹⁵ = 213898793 is a prime.

It is not a weakly prime, because it can be changed into another prime (213931511) 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, 106965780 + 106965781.

It is an arithmetic number, because the mean of its divisors is an integer number (106965781).

Almost surely, 2^213931561 is an apocalyptic number.

It is an amenable number.

213931561 is a deficient number, since it is larger than the sum of its proper divisors (1).

213931561 is an equidigital number, since it uses as much as digits as its factorization.

213931561 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 4860, while the sum is 31.

The square root of 213931561 is about 14626.3994544112. The cubic root of 213931561 is about 598.0786325163.

The spelling of 213931561 in words is "two hundred thirteen million, nine hundred thirty-one thousand, five hundred sixty-one".