261636437 has 2 divisors, whose sum is σ = 261636438. Its totient is φ = 261636436.

The previous prime is 261636433. The next prime is 261636439. The reversal of 261636437 is 734636162.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 255712081 + 5924356 = 15991^2 + 2434^2 .

It is a cyclic number.

It is not a de Polignac number, because 261636437 - 2² = 261636433 is a prime.

Together with 261636439, it forms a pair of twin primes.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 261636437.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (261636433) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 130818218 + 130818219.

It is an arithmetic number, because the mean of its divisors is an integer number (130818219).

Almost surely, 2^261636437 is an apocalyptic number.

It is an amenable number.

261636437 is a deficient number, since it is larger than the sum of its proper divisors (1).

261636437 is an equidigital number, since it uses as much as digits as its factorization.

261636437 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 108864, while the sum is 38.

The square root of 261636437 is about 16175.1796589713. The cubic root of 261636437 is about 639.5866772999.

The spelling of 261636437 in words is "two hundred sixty-one million, six hundred thirty-six thousand, four hundred thirty-seven".