261331640 has 32 divisors (see below), whose sum is σ = 601674480. Its totient is φ = 102100992.

The previous prime is 261331639. The next prime is 261331657. The reversal of 261331640 is 46133162.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 74249 + ... + 77688.

Almost surely, 2^261331640 is an apocalyptic number.

261331640 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

261331640 is an abundant number, since it is smaller than the sum of its proper divisors (340342840).

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

261331640 is a wasteful number, since it uses less digits than its factorization.

261331640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 151991 (or 151987 counting only the distinct ones).

The product of its (nonzero) digits is 2592, while the sum is 26.

The square root of 261331640 is about 16165.7551633074. The cubic root of 261331640 is about 639.3382156653.

The spelling of 261331640 in words is "two hundred sixty-one million, three hundred thirty-one thousand, six hundred forty".