261649019 has 4 divisors (see below), whose sum is σ = 275420040. Its totient is φ = 247878000.

The previous prime is 261649007. The next prime is 261649097. The reversal of 261649019 is 910946162.

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 261649019 - 2⁸ = 261648763 is a prime.

It is a super-2 number, since 2×261649019² = 136920418287324722, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (261649519) 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 3 ways as a sum of consecutive naturals, for example, 6885482 + ... + 6885519.

It is an arithmetic number, because the mean of its divisors is an integer number (68855010).

Almost surely, 2^261649019 is an apocalyptic number.

261649019 is a deficient number, since it is larger than the sum of its proper divisors (13771021).

261649019 is a wasteful number, since it uses less digits than its factorization.

261649019 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 13771020.

The product of its (nonzero) digits is 23328, while the sum is 38.

The square root of 261649019 is about 16175.5685835151. The cubic root of 261649019 is about 639.5969296316.

The spelling of 261649019 in words is "two hundred sixty-one million, six hundred forty-nine thousand, nineteen".