261220155 has 16 divisors (see below), whose sum is σ = 477659904. Its totient is φ = 119414880.

The previous prime is 261220153. The next prime is 261220187. The reversal of 261220155 is 551022162.

It is a happy number.

It is not a de Polignac number, because 261220155 - 2¹ = 261220153 is a prime.

It is not an unprimeable number, because it can be changed into a prime (261220153) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1243801 + ... + 1244010.

It is an arithmetic number, because the mean of its divisors is an integer number (29853744).

Almost surely, 2^261220155 is an apocalyptic number.

261220155 is a deficient number, since it is larger than the sum of its proper divisors (216439749).

261220155 is a wasteful number, since it uses less digits than its factorization.

261220155 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2487826.

The product of its (nonzero) digits is 1200, while the sum is 24.

The square root of 261220155 is about 16162.3066113720. The cubic root of 261220155 is about 639.2472880876.

The spelling of 261220155 in words is "two hundred sixty-one million, two hundred twenty thousand, one hundred fifty-five".