20641997 has 4 divisors (see below), whose sum is σ = 21353820. Its totient is φ = 19930176.

The previous prime is 20641993. The next prime is 20642009. The reversal of 20641997 is 79914602.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 79914602 = 2 ⋅39957301.

It can be written as a sum of positive squares in 2 ways, for example, as 11485321 + 9156676 = 3389^2 + 3026^2 .

It is a cyclic number.

It is not a de Polignac number, because 20641997 - 2² = 20641993 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 20641997.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20641993) 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, 355868 + ... + 355925.

It is an arithmetic number, because the mean of its divisors is an integer number (5338455).

Almost surely, 2^20641997 is an apocalyptic number.

It is an amenable number.

20641997 is a deficient number, since it is larger than the sum of its proper divisors (711823).

20641997 is an equidigital number, since it uses as much as digits as its factorization.

20641997 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 711822.

The product of its (nonzero) digits is 27216, while the sum is 38.

The square root of 20641997 is about 4543.3464538818. The cubic root of 20641997 is about 274.3156404780.

The spelling of 20641997 in words is "twenty million, six hundred forty-one thousand, nine hundred ninety-seven".