1239947991 has 6 divisors (see below), whose sum is σ = 1791036000. Its totient is φ = 826631988.

The previous prime is 1239947977. The next prime is 1239948001. The reversal of 1239947991 is 1997499321.

It is a happy number.

It is not a de Polignac number, because 1239947991 - 2⁶ = 1239947927 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1239947941) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 68885991 + ... + 68886008.

It is an arithmetic number, because the mean of its divisors is an integer number (298506000).

Almost surely, 2^1239947991 is an apocalyptic number.

1239947991 is a deficient number, since it is larger than the sum of its proper divisors (551088009).

1239947991 is a wasteful number, since it uses less digits than its factorization.

1239947991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 137772005 (or 137772002 counting only the distinct ones).

The product of its digits is 1102248, while the sum is 54.

The square root of 1239947991 is about 35212.8952373985. The cubic root of 1239947991 is about 1074.3220505648.

The spelling of 1239947991 in words is "one billion, two hundred thirty-nine million, nine hundred forty-seven thousand, nine hundred ninety-one".