406991 has 4 divisors (see below), whose sum is σ = 438312. Its totient is φ = 375672.

The previous prime is 406981. The next prime is 406993. The reversal of 406991 is 199604.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 406991 - 2¹⁰ = 405967 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (406993) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 15641 + ... + 15666.

It is an arithmetic number, because the mean of its divisors is an integer number (109578).

2⁴⁰⁶⁹⁹¹ is an apocalyptic number.

406991 is a deficient number, since it is larger than the sum of its proper divisors (31321).

406991 is a wasteful number, since it uses less digits than its factorization.

406991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 31320.

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

The square root of 406991 is about 637.9584625977. The cubic root of 406991 is about 74.1074042999.

The spelling of 406991 in words is "four hundred six thousand, nine hundred ninety-one".