261651217 has 4 divisors (see below), whose sum is σ = 268032996. Its totient is φ = 255269440.

The previous prime is 261651211. The next prime is 261651251. The reversal of 261651217 is 712156162.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 122788561 + 138862656 = 11081^2 + 11784^2 .

It is a cyclic number.

It is not a de Polignac number, because 261651217 - 2¹¹ = 261649169 is a prime.

It is a super-2 number, since 2×261651217² = 136922718715162178, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (261651211) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3190828 + ... + 3190909.

It is an arithmetic number, because the mean of its divisors is an integer number (67008249).

Almost surely, 2^261651217 is an apocalyptic number.

It is an amenable number.

261651217 is a deficient number, since it is larger than the sum of its proper divisors (6381779).

261651217 is an equidigital number, since it uses as much as digits as its factorization.

261651217 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6381778.

The product of its digits is 5040, while the sum is 31.

The square root of 261651217 is about 16175.6365253427. The cubic root of 261651217 is about 639.5987206188.

The spelling of 261651217 in words is "two hundred sixty-one million, six hundred fifty-one thousand, two hundred seventeen".