261921285 has 12 divisors (see below), whose sum is σ = 453996972. Its totient is φ = 139691328.

The previous prime is 261921281. The next prime is 261921287. The reversal of 261921285 is 582129162.

261921285 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It can be written as a sum of positive squares in 2 ways, for example, as 43797924 + 218123361 = 6618^2 + 14769^2 .

It is not a de Polignac number, because 261921285 - 2² = 261921281 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (261921281) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 2910192 + ... + 2910281.

It is an arithmetic number, because the mean of its divisors is an integer number (37833081).

Almost surely, 2^261921285 is an apocalyptic number.

It is an amenable number.

261921285 is a deficient number, since it is larger than the sum of its proper divisors (192075687).

261921285 is a wasteful number, since it uses less digits than its factorization.

261921285 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5820484 (or 5820481 counting only the distinct ones).

The product of its digits is 17280, while the sum is 36.

The square root of 261921285 is about 16183.9823591105. The cubic root of 261921285 is about 639.8187027165.

The spelling of 261921285 in words is "two hundred sixty-one million, nine hundred twenty-one thousand, two hundred eighty-five".