261663481 has 2 divisors, whose sum is σ = 261663482. Its totient is φ = 261663480.

The previous prime is 261663397. The next prime is 261663487. The reversal of 261663481 is 184366162.

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., 255488256 + 6175225 = 15984^2 + 2485^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-261663481 is a prime.

It is a super-2 number, since 2×261663481² = 136935554578074722, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 261663481.

It is not a weakly prime, because it can be changed into another prime (261663487) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 130831740 + 130831741.

It is an arithmetic number, because the mean of its divisors is an integer number (130831741).

Almost surely, 2^261663481 is an apocalyptic number.

It is an amenable number.

261663481 is a deficient number, since it is larger than the sum of its proper divisors (1).

261663481 is an equidigital number, since it uses as much as digits as its factorization.

261663481 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 41472, while the sum is 37.

The square root of 261663481 is about 16176.0156095375. The cubic root of 261663481 is about 639.6087134587.

It can be divided in two parts, 261663 and 481, that added together give a 18-th power (262144 = 2¹⁸).

The spelling of 261663481 in words is "two hundred sixty-one million, six hundred sixty-three thousand, four hundred eighty-one".