261663969 has 12 divisors (see below), whose sum is σ = 405846384. Its totient is φ = 149522184.

The previous prime is 261663967. The next prime is 261663973. The reversal of 261663969 is 969366162.

It is a happy number.

It is not a de Polignac number, because 261663969 - 2¹ = 261663967 is a prime.

It is a super-2 number, since 2×261663969² = 136936065345665922, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (261663967) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 889867 + ... + 890160.

It is an arithmetic number, because the mean of its divisors is an integer number (33820532).

Almost surely, 2^261663969 is an apocalyptic number.

It is an amenable number.

261663969 is a deficient number, since it is larger than the sum of its proper divisors (144182415).

261663969 is a wasteful number, since it uses less digits than its factorization.

261663969 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1780044 (or 1780037 counting only the distinct ones).

The product of its digits is 629856, while the sum is 48.

The square root of 261663969 is about 16176.0306935911. The cubic root of 261663969 is about 639.6091110799.

It can be divided in two parts, 26166 and 3969, that added together give a triangular number (30135 = T₂₄₅).

The spelling of 261663969 in words is "two hundred sixty-one million, six hundred sixty-three thousand, nine hundred sixty-nine".