261512749 has 4 divisors (see below), whose sum is σ = 270530460. Its totient is φ = 252495040.

The previous prime is 261512743. The next prime is 261512761. The reversal of 261512749 is 947215162.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 111450249 + 150062500 = 10557^2 + 12250^2 .

It is a cyclic number.

It is not a de Polignac number, because 261512749 - 2¹⁹ = 260988461 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (261512743) 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 in 3 ways as a sum of consecutive naturals, for example, 4508812 + ... + 4508869.

It is an arithmetic number, because the mean of its divisors is an integer number (67632615).

Almost surely, 2^261512749 is an apocalyptic number.

261512749 is a gapful number since it is divisible by the number (29) formed by its first and last digit.

It is an amenable number.

261512749 is a deficient number, since it is larger than the sum of its proper divisors (9017711).

261512749 is an equidigital number, since it uses as much as digits as its factorization.

261512749 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9017710.

The product of its digits is 30240, while the sum is 37.

The square root of 261512749 is about 16171.3558182361. The cubic root of 261512749 is about 639.4858737226.

It can be divided in two parts, 26151 and 2749, that added together give a square (28900 = 170²).

The spelling of 261512749 in words is "two hundred sixty-one million, five hundred twelve thousand, seven hundred forty-nine".