261553331 has 4 divisors (see below), whose sum is σ = 281672832. Its totient is φ = 241433832.

The previous prime is 261553319. The next prime is 261553339. The reversal of 261553331 is 133355162.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 133355162 = 2 ⋅66677581.

It is a cyclic number.

It is not a de Polignac number, because 261553331 - 2¹⁰ = 261552307 is a prime.

It is a super-2 number, since 2×261553331² = 136820289914391122, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 261553294 and 261553303.

It is not an unprimeable number, because it can be changed into a prime (261553339) 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, 10059731 + ... + 10059756.

It is an arithmetic number, because the mean of its divisors is an integer number (70418208).

Almost surely, 2^261553331 is an apocalyptic number.

261553331 is a deficient number, since it is larger than the sum of its proper divisors (20119501).

261553331 is a wasteful number, since it uses less digits than its factorization.

261553331 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 20119500.

The product of its digits is 8100, while the sum is 29.

The square root of 261553331 is about 16172.6105190226. The cubic root of 261553331 is about 639.5189508524.

The spelling of 261553331 in words is "two hundred sixty-one million, five hundred fifty-three thousand, three hundred thirty-one".