261809291 has 8 divisors (see below), whose sum is σ = 270941568. Its totient is φ = 252720000.

The previous prime is 261809287. The next prime is 261809309. The reversal of 261809291 is 192908162.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 261809291 - 2² = 261809287 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (261809221) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1901 + ... + 22961.

It is an arithmetic number, because the mean of its divisors is an integer number (33867696).

Almost surely, 2^261809291 is an apocalyptic number.

261809291 is a deficient number, since it is larger than the sum of its proper divisors (9132277).

261809291 is a wasteful number, since it uses less digits than its factorization.

261809291 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 21493.

The product of its (nonzero) digits is 15552, while the sum is 38.

The square root of 261809291 is about 16180.5219631506. The cubic root of 261809291 is about 639.7274971071.

The spelling of 261809291 in words is "two hundred sixty-one million, eight hundred nine thousand, two hundred ninety-one".