261177921 has 9 divisors (see below), whose sum is σ = 377327041. Its totient is φ = 174086292.

The previous prime is 261177901. The next prime is 261177923. The reversal of 261177921 is 129771162.

It is a happy number.

The square root of 261177921 is 16161.

It is a perfect power (a square), and thus also a powerful number.

It is a tau number, because it is divible by the number of its divisors (9).

It is a de Polignac number, because none of the positive numbers 2^k-261177921 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (261177923) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 45790 + ... + 51176.

Almost surely, 2^261177921 is an apocalyptic number.

261177921 is the 16161-st square number.

261177921 is the 8081-st centered octagonal number.

It is an amenable number.

261177921 is a deficient number, since it is larger than the sum of its proper divisors (116149120).

261177921 is an frugal number, since it uses more digits than its factorization.

261177921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10780 (or 5390 counting only the distinct ones).

The product of its digits is 10584, while the sum is 36.

The cubic root of 261177921 is about 639.2128351245.

Multiplying 261177921 by its sum of digits (36), we get a square (9402405156 = 96966²).

The spelling of 261177921 in words is "two hundred sixty-one million, one hundred seventy-seven thousand, nine hundred twenty-one".