261216643 has 4 divisors (see below), whose sum is σ = 261298440. Its totient is φ = 261134848.

The previous prime is 261216619. The next prime is 261216673. The reversal of 261216643 is 346612162.

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

It is a cyclic number.

It is not a de Polignac number, because 261216643 - 2¹⁷ = 261085571 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (261216673) 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, 35905 + ... + 42562.

It is an arithmetic number, because the mean of its divisors is an integer number (65324610).

Almost surely, 2^261216643 is an apocalyptic number.

261216643 is a deficient number, since it is larger than the sum of its proper divisors (81797).

261216643 is an equidigital number, since it uses as much as digits as its factorization.

261216643 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 81796.

The product of its digits is 10368, while the sum is 31.

The square root of 261216643 is about 16162.1979631485. The cubic root of 261216643 is about 639.2444232671.

The spelling of 261216643 in words is "two hundred sixty-one million, two hundred sixteen thousand, six hundred forty-three".