261787511 has 4 divisors (see below), whose sum is σ = 266726952. Its totient is φ = 256848072.

The previous prime is 261787507. The next prime is 261787517. The reversal of 261787511 is 115787162.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 115787162 = 2 ⋅57893581.

It is a cyclic number.

It is not a de Polignac number, because 261787511 - 2² = 261787507 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (261787517) 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 in 3 ways as a sum of consecutive naturals, for example, 2469641 + ... + 2469746.

It is an arithmetic number, because the mean of its divisors is an integer number (66681738).

Almost surely, 2^261787511 is an apocalyptic number.

261787511 is a deficient number, since it is larger than the sum of its proper divisors (4939441).

261787511 is an equidigital number, since it uses as much as digits as its factorization.

261787511 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4939440.

The product of its digits is 23520, while the sum is 38.

The square root of 261787511 is about 16179.8489177124. The cubic root of 261787511 is about 639.7097569024.

The spelling of 261787511 in words is "two hundred sixty-one million, seven hundred eighty-seven thousand, five hundred eleven".