261561651 has 8 divisors (see below), whose sum is σ = 375575760. Its totient is φ = 160960992.

The previous prime is 261561637. The next prime is 261561661. The reversal of 261561651 is 156165162.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 261561651 - 2¹⁰ = 261560627 is a prime.

It is not an unprimeable number, because it can be changed into a prime (261561611) 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 7 ways as a sum of consecutive naturals, for example, 3353316 + ... + 3353393.

It is an arithmetic number, because the mean of its divisors is an integer number (46946970).

Almost surely, 2^261561651 is an apocalyptic number.

261561651 is a deficient number, since it is larger than the sum of its proper divisors (114014109).

261561651 is a wasteful number, since it uses less digits than its factorization.

261561651 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6706725.

The product of its digits is 10800, while the sum is 33.

The square root of 261561651 is about 16172.8677419931. The cubic root of 261561651 is about 639.5257318038.

The spelling of 261561651 in words is "two hundred sixty-one million, five hundred sixty-one thousand, six hundred fifty-one".