1261138398 has 24 divisors (see below), whose sum is σ = 2716973784. Its totient is φ = 387946080.

The previous prime is 1261138391. The next prime is 1261138427. The reversal of 1261138398 is 8938311621.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1261138391) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 311628 + ... + 315648.

It is an arithmetic number, because the mean of its divisors is an integer number (113207241).

Almost surely, 2^1261138398 is an apocalyptic number.

1261138398 is an abundant number, since it is smaller than the sum of its proper divisors (1455835386).

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

1261138398 is an frugal number, since it uses more digits than its factorization.

1261138398 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8060 (or 4039 counting only the distinct ones).

The product of its digits is 62208, while the sum is 42.

The square root of 1261138398 is about 35512.5104435043. The cubic root of 1261138398 is about 1080.4074816982.

The spelling of 1261138398 in words is "one billion, two hundred sixty-one million, one hundred thirty-eight thousand, three hundred ninety-eight".