1261271440 has 80 divisors (see below), whose sum is σ = 3445154496. Its totient is φ = 423360000.

The previous prime is 1261271437. The next prime is 1261271483. The reversal of 1261271440 is 441721621.

It is a tau number, because it is divible by the number of its divisors (80).

It is a junction number, because it is equal to n+sod(n) for n = 1261271399 and 1261271408.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 43686 + ... + 66565.

Almost surely, 2^1261271440 is an apocalyptic number.

1261271440 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

1261271440 is an abundant number, since it is smaller than the sum of its proper divisors (2183883056).

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

1261271440 is a wasteful number, since it uses less digits than its factorization.

1261271440 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 110288 (or 110282 counting only the distinct ones).

The product of its (nonzero) digits is 2688, while the sum is 28.

The square root of 1261271440 is about 35514.3835649727. The cubic root of 1261271440 is about 1080.4454723788.

The spelling of 1261271440 in words is "one billion, two hundred sixty-one million, two hundred seventy-one thousand, four hundred forty".