20811691 has 2 divisors, whose sum is σ = 20811692. Its totient is φ = 20811690.

The previous prime is 20811667. The next prime is 20811731. The reversal of 20811691 is 19611802.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 20811691 - 2¹¹ = 20809643 is a prime.

It is not a weakly prime, because it can be changed into another prime (20811611) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10405845 + 10405846.

It is an arithmetic number, because the mean of its divisors is an integer number (10405846).

Almost surely, 2^20811691 is an apocalyptic number.

20811691 is a deficient number, since it is larger than the sum of its proper divisors (1).

20811691 is an equidigital number, since it uses as much as digits as its factorization.

20811691 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 864, while the sum is 28.

The square root of 20811691 is about 4561.9832310082. The cubic root of 20811691 is about 275.0652891813.

The spelling of 20811691 in words is "twenty million, eight hundred eleven thousand, six hundred ninety-one".