20990357 has 4 divisors (see below), whose sum is σ = 21000876. Its totient is φ = 20979840.

The previous prime is 20990353. The next prime is 20990399. The reversal of 20990357 is 75309902.

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, and also an emirpimes, since its reverse is a distinct semiprime: 75309902 = 2 ⋅37654951.

It can be written as a sum of positive squares in 2 ways, for example, as 2961841 + 18028516 = 1721^2 + 4246^2 .

It is a cyclic number.

It is not a de Polignac number, because 20990357 - 2² = 20990353 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20990353) 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, 1244 + ... + 6597.

It is an arithmetic number, because the mean of its divisors is an integer number (5250219).

Almost surely, 2^20990357 is an apocalyptic number.

It is an amenable number.

20990357 is a deficient number, since it is larger than the sum of its proper divisors (10519).

20990357 is an equidigital number, since it uses as much as digits as its factorization.

20990357 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10518.

The product of its (nonzero) digits is 17010, while the sum is 35.

The square root of 20990357 is about 4581.5234365874. The cubic root of 20990357 is about 275.8501821159.

The spelling of 20990357 in words is "twenty million, nine hundred ninety thousand, three hundred fifty-seven".