991406 has 16 divisors (see below), whose sum is σ = 1696464. Its totient is φ = 430464.

The previous prime is 991387. The next prime is 991409. The reversal of 991406 is 604199.

991406 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is an Ulam number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (991409) by changing a digit.

991406 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 680 + ... + 1563.

It is an arithmetic number, because the mean of its divisors is an integer number (106029).

2⁹⁹¹⁴⁰⁶ is an apocalyptic number.

991406 is a deficient number, since it is larger than the sum of its proper divisors (705058).

991406 is a wasteful number, since it uses less digits than its factorization.

991406 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2275.

The product of its (nonzero) digits is 1944, while the sum is 29.

The square root of 991406 is about 995.6937280108. The cubic root of 991406 is about 99.7127087612.

The spelling of 991406 in words is "nine hundred ninety-one thousand, four hundred six".