20161691 has 4 divisors (see below), whose sum is σ = 21994584. Its totient is φ = 18328800.

The previous prime is 20161667. The next prime is 20161693. The reversal of 20161691 is 19616102.

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 20161691 - 2¹⁰ = 20160667 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 20161691.

It is not an unprimeable number, because it can be changed into a prime (20161693) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 916430 + ... + 916451.

It is an arithmetic number, because the mean of its divisors is an integer number (5498646).

Almost surely, 2^20161691 is an apocalyptic number.

20161691 is a deficient number, since it is larger than the sum of its proper divisors (1832893).

20161691 is a wasteful number, since it uses less digits than its factorization.

20161691 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1832892.

The product of its (nonzero) digits is 648, while the sum is 26.

The square root of 20161691 is about 4490.1771679968. The cubic root of 20161691 is about 272.1712940284.

Adding to 20161691 its reverse (19616102), we get a palindrome (39777793).

The spelling of 20161691 in words is "twenty million, one hundred sixty-one thousand, six hundred ninety-one".