261129551 has 4 divisors (see below), whose sum is σ = 264807504. Its totient is φ = 257451600.

The previous prime is 261129527. The next prime is 261129563. The reversal of 261129551 is 155921162.

261129551 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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

It is a cyclic number.

It is not a de Polignac number, because 261129551 - 2²² = 256935247 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 (261120551) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1838870 + ... + 1839011.

It is an arithmetic number, because the mean of its divisors is an integer number (66201876).

Almost surely, 2^261129551 is an apocalyptic number.

261129551 is a deficient number, since it is larger than the sum of its proper divisors (3677953).

261129551 is an equidigital number, since it uses as much as digits as its factorization.

261129551 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3677952.

The product of its digits is 5400, while the sum is 32.

The square root of 261129551 is about 16159.5034267765. The cubic root of 261129551 is about 639.1733720723.

The spelling of 261129551 in words is "two hundred sixty-one million, one hundred twenty-nine thousand, five hundred fifty-one".