1261005399 has 12 divisors (see below), whose sum is σ = 1870681176. Its totient is φ = 817949232.

The previous prime is 1261005397. The next prime is 1261005409. The reversal of 1261005399 is 9935001621.

1261005399 is a `hidden beast` number, since 1 + 2 + 610 + 0 + 5 + 39 + 9 = 666.

It is not a de Polignac number, because 1261005399 - 2¹ = 1261005397 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1261005391) 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, 1893069 + ... + 1893734.

It is an arithmetic number, because the mean of its divisors is an integer number (155890098).

Almost surely, 2^1261005399 is an apocalyptic number.

1261005399 is a deficient number, since it is larger than the sum of its proper divisors (609675777).

1261005399 is a wasteful number, since it uses less digits than its factorization.

1261005399 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3786846 (or 3786843 counting only the distinct ones).

The product of its (nonzero) digits is 14580, while the sum is 36.

The square root of 1261005399 is about 35510.6378286845. The cubic root of 1261005399 is about 1080.3695006259.

The spelling of 1261005399 in words is "one billion, two hundred sixty-one million, five thousand, three hundred ninety-nine".