261311621 has 2 divisors, whose sum is σ = 261311622. Its totient is φ = 261311620.

The previous prime is 261311599. The next prime is 261311627. The reversal of 261311621 is 126113162.

261311621 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 146071396 + 115240225 = 12086^2 + 10735^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-261311621 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (261311627) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 130655810 + 130655811.

It is an arithmetic number, because the mean of its divisors is an integer number (130655811).

Almost surely, 2^261311621 is an apocalyptic number.

It is an amenable number.

261311621 is a deficient number, since it is larger than the sum of its proper divisors (1).

261311621 is an equidigital number, since it uses as much as digits as its factorization.

261311621 is an evil number, because the sum of its binary digits is even.

The product of its digits is 432, while the sum is 23.

The square root of 261311621 is about 16165.1359722088. The cubic root of 261311621 is about 639.3218900001.

Adding to 261311621 its reverse (126113162), we get a palindrome (387424783).

The spelling of 261311621 in words is "two hundred sixty-one million, three hundred eleven thousand, six hundred twenty-one".