261388640 has 24 divisors (see below), whose sum is σ = 617531040. Its totient is φ = 104555392.

The previous prime is 261388619. The next prime is 261388661. The reversal of 261388640 is 46883162.

It is a happy number.

261388640 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is an interprime number because it is at equal distance from previous prime (261388619) and next prime (261388661).

It is a super-2 number, since 2×261388640² = 136648042242099200, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 261388594 and 261388603.

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, 816680 + ... + 816999.

It is an arithmetic number, because the mean of its divisors is an integer number (25730460).

Almost surely, 2^261388640 is an apocalyptic number.

261388640 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

261388640 is an abundant number, since it is smaller than the sum of its proper divisors (356142400).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

261388640 is a wasteful number, since it uses less digits than its factorization.

261388640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1633694 (or 1633686 counting only the distinct ones).

The product of its (nonzero) digits is 55296, while the sum is 38.

The square root of 261388640 is about 16167.5180531831. The cubic root of 261388640 is about 639.3846950852.

The spelling of 261388640 in words is "two hundred sixty-one million, three hundred eighty-eight thousand, six hundred forty".