261539771 has 2 divisors, whose sum is σ = 261539772. Its totient is φ = 261539770.

The previous prime is 261539749. The next prime is 261539783. The reversal of 261539771 is 177935162.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 261539771 - 2²² = 257345467 is a prime.

It is not a weakly prime, because it can be changed into another prime (261539171) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 130769885 + 130769886.

It is an arithmetic number, because the mean of its divisors is an integer number (130769886).

Almost surely, 2^261539771 is an apocalyptic number.

261539771 is a deficient number, since it is larger than the sum of its proper divisors (1).

261539771 is an equidigital number, since it uses as much as digits as its factorization.

261539771 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 79380, while the sum is 41.

The square root of 261539771 is about 16172.1912862790. The cubic root of 261539771 is about 639.5078988975.

The spelling of 261539771 in words is "two hundred sixty-one million, five hundred thirty-nine thousand, seven hundred seventy-one".