20681491 has 2 divisors, whose sum is σ = 20681492. Its totient is φ = 20681490.

The previous prime is 20681477. The next prime is 20681497. The reversal of 20681491 is 19418602.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 20681491 - 2⁵ = 20681459 is a prime.

It is not a weakly prime, because it can be changed into another prime (20681497) 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 as a sum of consecutive naturals, namely, 10340745 + 10340746.

It is an arithmetic number, because the mean of its divisors is an integer number (10340746).

Almost surely, 2^20681491 is an apocalyptic number.

20681491 is a deficient number, since it is larger than the sum of its proper divisors (1).

20681491 is an equidigital number, since it uses as much as digits as its factorization.

20681491 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 3456, while the sum is 31.

The square root of 20681491 is about 4547.6907326686. The cubic root of 20681491 is about 274.4904769186.

The spelling of 20681491 in words is "twenty million, six hundred eighty-one thousand, four hundred ninety-one".