261655553 has 4 divisors (see below), whose sum is σ = 264101040. Its totient is φ = 259210068.

The previous prime is 261655543. The next prime is 261655561. The reversal of 261655553 is 355556162.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 261655553 - 2²⁶ = 194546689 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (261655543) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1222583 + ... + 1222796.

It is an arithmetic number, because the mean of its divisors is an integer number (66025260).

Almost surely, 2^261655553 is an apocalyptic number.

It is an amenable number.

261655553 is a deficient number, since it is larger than the sum of its proper divisors (2445487).

261655553 is a wasteful number, since it uses less digits than its factorization.

261655553 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2445486.

The product of its digits is 135000, while the sum is 38.

The square root of 261655553 is about 16175.7705535161. The cubic root of 261655553 is about 639.6022536742.

The spelling of 261655553 in words is "two hundred sixty-one million, six hundred fifty-five thousand, five hundred fifty-three".