261778672 has 20 divisors (see below), whose sum is σ = 507764376. Its totient is φ = 130742720.

The previous prime is 261778667. The next prime is 261778681. The reversal of 261778672 is 276877162.

It is a super-2 number, since 2×261778672² = 137056146228167168, which contains 22 as substring.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 6363 + ... + 23749.

Almost surely, 2^261778672 is an apocalyptic number.

It is an amenable number.

261778672 is a deficient number, since it is larger than the sum of its proper divisors (245985704).

261778672 is a wasteful number, since it uses less digits than its factorization.

261778672 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 18336 (or 18330 counting only the distinct ones).

The product of its digits is 395136, while the sum is 46.

The square root of 261778672 is about 16179.5757669971. The cubic root of 261778672 is about 639.7025570960.

It can be divided in two parts, 261778 and 672, that added together give a triangular number (262450 = T₇₂₄).

The spelling of 261778672 in words is "two hundred sixty-one million, seven hundred seventy-eight thousand, six hundred seventy-two".