20791821 has 4 divisors (see below), whose sum is σ = 27722432. Its totient is φ = 13861212.

The previous prime is 20791819. The next prime is 20791831. The reversal of 20791821 is 12819702.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 20791821 - 2¹ = 20791819 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20791801) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3465301 + ... + 3465306.

It is an arithmetic number, because the mean of its divisors is an integer number (6930608).

Almost surely, 2^20791821 is an apocalyptic number.

It is an amenable number.

20791821 is a deficient number, since it is larger than the sum of its proper divisors (6930611).

20791821 is an equidigital number, since it uses as much as digits as its factorization.

20791821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6930610.

The product of its (nonzero) digits is 2016, while the sum is 30.

The square root of 20791821 is about 4559.8049300381. The cubic root of 20791821 is about 274.9777216112.

It can be divided in two parts, 20791 and 821, that added together give a palindrome (21612).

The spelling of 20791821 in words is "twenty million, seven hundred ninety-one thousand, eight hundred twenty-one".