20821797 has 12 divisors (see below), whose sum is σ = 31113420. Its totient is φ = 13402368.

The previous prime is 20821789. The next prime is 20821841. The reversal of 20821797 is 79712802.

It can be written as a sum of positive squares in 2 ways, for example, as 15374241 + 5447556 = 3921^2 + 2334^2 .

It is not a de Polignac number, because 20821797 - 2³ = 20821789 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20821747) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 39628 + ... + 40149.

It is an arithmetic number, because the mean of its divisors is an integer number (2592785).

Almost surely, 2^20821797 is an apocalyptic number.

It is an amenable number.

20821797 is a deficient number, since it is larger than the sum of its proper divisors (10291623).

20821797 is a wasteful number, since it uses less digits than its factorization.

20821797 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 79812 (or 79809 counting only the distinct ones).

The product of its (nonzero) digits is 14112, while the sum is 36.

The square root of 20821797 is about 4563.0907288810. The cubic root of 20821797 is about 275.1098051857.

The spelling of 20821797 in words is "twenty million, eight hundred twenty-one thousand, seven hundred ninety-seven".