261078921 has 12 divisors (see below), whose sum is σ = 377475072. Its totient is φ = 173885976.

The previous prime is 261078887. The next prime is 261078959. The reversal of 261078921 is 129870162.

It is not a de Polignac number, because 261078921 - 2¹¹ = 261076873 is a prime.

It is not an unprimeable number, because it can be changed into a prime (261078721) 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 11 ways as a sum of consecutive naturals, for example, 3561 + ... + 23126.

It is an arithmetic number, because the mean of its divisors is an integer number (31456256).

Almost surely, 2^261078921 is an apocalyptic number.

It is an amenable number.

261078921 is a deficient number, since it is larger than the sum of its proper divisors (116396151).

261078921 is a wasteful number, since it uses less digits than its factorization.

261078921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 27780 (or 27777 counting only the distinct ones).

The product of its (nonzero) digits is 12096, while the sum is 36.

The square root of 261078921 is about 16157.9367804185. The cubic root of 261078921 is about 639.1320599606.

The spelling of 261078921 in words is "two hundred sixty-one million, seventy-eight thousand, nine hundred twenty-one".