311561 has 2 divisors, whose sum is σ = 311562. Its totient is φ = 311560.

The previous prime is 311557. The next prime is 311567. The reversal of 311561 is 165113.

311561 is nontrivially palindromic in base 8.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 295936 + 15625 = 544^2 + 125^2 .

It is a cyclic number.

It is not a de Polignac number, because 311561 - 2² = 311557 is a prime.

It is not a weakly prime, because it can be changed into another prime (311567) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 155780 + 155781.

It is an arithmetic number, because the mean of its divisors is an integer number (155781).

2³¹¹⁵⁶¹ is an apocalyptic number.

It is an amenable number.

311561 is a deficient number, since it is larger than the sum of its proper divisors (1).

311561 is an equidigital number, since it uses as much as digits as its factorization.

311561 is an evil number, because the sum of its binary digits is even.

The product of its digits is 90, while the sum is 17.

The square root of 311561 is about 558.1764953847. The cubic root of 311561 is about 67.7924032061.

Adding to 311561 its reverse (165113), we get a palindrome (476674).

It can be divided in two parts, 311 and 561, that multiplied together give a palindrome (174471).

The spelling of 311561 in words is "three hundred eleven thousand, five hundred sixty-one".