261533649 has 16 divisors (see below), whose sum is σ = 385687232. Its totient is φ = 156593088.

The previous prime is 261533633. The next prime is 261533693. The reversal of 261533649 is 946335162.

It is not a de Polignac number, because 261533649 - 2⁴ = 261533633 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (39).

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (261533609) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 89179 + ... + 92064.

It is an arithmetic number, because the mean of its divisors is an integer number (24105452).

Almost surely, 2^261533649 is an apocalyptic number.

It is an amenable number.

261533649 is a deficient number, since it is larger than the sum of its proper divisors (124153583).

261533649 is a wasteful number, since it uses less digits than its factorization.

261533649 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 181296.

The product of its digits is 116640, while the sum is 39.

The square root of 261533649 is about 16172.0020096462. The cubic root of 261533649 is about 639.5029090918.

The spelling of 261533649 in words is "two hundred sixty-one million, five hundred thirty-three thousand, six hundred forty-nine".