261221205 has 48 divisors (see below), whose sum is σ = 490083264. Its totient is φ = 118460160.

The previous prime is 261221203. The next prime is 261221237. The reversal of 261221205 is 502122162.

It is a happy number.

It is not a de Polignac number, because 261221205 - 2¹ = 261221203 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (21).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (261221203) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 94929 + ... + 97641.

It is an arithmetic number, because the mean of its divisors is an integer number (10210068).

Almost surely, 2^261221205 is an apocalyptic number.

It is an amenable number.

261221205 is a deficient number, since it is larger than the sum of its proper divisors (228862059).

261221205 is a wasteful number, since it uses less digits than its factorization.

261221205 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2866 (or 2859 counting only the distinct ones).

The product of its (nonzero) digits is 480, while the sum is 21.

The square root of 261221205 is about 16162.3390943267. The cubic root of 261221205 is about 639.2481445921.

Adding to 261221205 its reverse (502122162), we get a palindrome (763343367).

The spelling of 261221205 in words is "two hundred sixty-one million, two hundred twenty-one thousand, two hundred five".