261221855 has 16 divisors (see below), whose sum is σ = 319140864. Its totient is φ = 205228800.

The previous prime is 261221819. The next prime is 261221929. The reversal of 261221855 is 558122162.

It is not a de Polignac number, because 261221855 - 2¹⁴ = 261205471 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 62099 + ... + 66171.

It is an arithmetic number, because the mean of its divisors is an integer number (19946304).

Almost surely, 2^261221855 is an apocalyptic number.

261221855 is a deficient number, since it is larger than the sum of its proper divisors (57919009).

261221855 is a wasteful number, since it uses less digits than its factorization.

261221855 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4306.

The product of its digits is 9600, while the sum is 32.

The square root of 261221855 is about 16162.3592027897. The cubic root of 261221855 is about 639.2486748081.

The spelling of 261221855 in words is "two hundred sixty-one million, two hundred twenty-one thousand, eight hundred fifty-five".