406821691 has 4 divisors (see below), whose sum is σ = 406862352. Its totient is φ = 406781032.

The previous prime is 406821689. The next prime is 406821731. The reversal of 406821691 is 196128604.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 406821691 - 2¹ = 406821689 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 406821691.

It is not an unprimeable number, because it can be changed into a prime (406821601) 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, 6345 + ... + 29221.

It is an arithmetic number, because the mean of its divisors is an integer number (101715588).

Almost surely, 2^406821691 is an apocalyptic number.

406821691 is a deficient number, since it is larger than the sum of its proper divisors (40661).

406821691 is a wasteful number, since it uses less digits than its factorization.

406821691 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 40660.

The product of its (nonzero) digits is 20736, while the sum is 37.

The square root of 406821691 is about 20169.8212932093. The cubic root of 406821691 is about 740.9712660273.

The spelling of 406821691 in words is "four hundred six million, eight hundred twenty-one thousand, six hundred ninety-one".