1991291406 has 16 divisors (see below), whose sum is σ = 4288935504. Its totient is φ = 612705024.

The previous prime is 1991291399. The next prime is 1991291513. The reversal of 1991291406 is 6041921991.

It is a happy number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 12764611 + ... + 12764766.

It is an arithmetic number, because the mean of its divisors is an integer number (268058469).

Almost surely, 2^1991291406 is an apocalyptic number.

1991291406 is an abundant number, since it is smaller than the sum of its proper divisors (2297644098).

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

1991291406 is a wasteful number, since it uses less digits than its factorization.

1991291406 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 25529395.

The product of its (nonzero) digits is 34992, while the sum is 42.

The square root of 1991291406 is about 44623.8882886734. Note that the first 3 decimals coincide. The cubic root of 1991291406 is about 1258.0896990862.

The spelling of 1991291406 in words is "one billion, nine hundred ninety-one million, two hundred ninety-one thousand, four hundred six".