1261031640 has 128 divisors (see below), whose sum is σ = 4260280320. Its totient is φ = 295833600.

The previous prime is 1261031623. The next prime is 1261031677. The reversal of 1261031640 is 461301621.

It is a Harshad number since it is a multiple of its sum of digits (24).

It is a self number, because there is not a number n which added to its sum of digits gives 1261031640.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 25512 + ... + 56328.

It is an arithmetic number, because the mean of its divisors is an integer number (33283440).

Almost surely, 2^1261031640 is an apocalyptic number.

1261031640 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 1261031640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (2130140160).

1261031640 is an abundant number, since it is smaller than the sum of its proper divisors (2999248680).

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

1261031640 is a wasteful number, since it uses less digits than its factorization.

1261031640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 30873 (or 30869 counting only the distinct ones).

The product of its (nonzero) digits is 864, while the sum is 24.

The square root of 1261031640 is about 35511.0073075941. The cubic root of 1261031640 is about 1080.3769945878.

It can be divided in two parts, 126 and 1031640, that added together give a triangular number (1031766 = T₁₄₃₆).

The spelling of 1261031640 in words is "one billion, two hundred sixty-one million, thirty-one thousand, six hundred forty".