20821789 has 2 divisors, whose sum is σ = 20821790. Its totient is φ = 20821788.

The previous prime is 20821763. The next prime is 20821841. The reversal of 20821789 is 98712802.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 19980900 + 840889 = 4470^2 + 917^2 .

It is a cyclic number.

It is not a de Polignac number, because 20821789 - 2²¹ = 18724637 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20821709) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10410894 + 10410895.

It is an arithmetic number, because the mean of its divisors is an integer number (10410895).

Almost surely, 2^20821789 is an apocalyptic number.

It is an amenable number.

20821789 is a deficient number, since it is larger than the sum of its proper divisors (1).

20821789 is an equidigital number, since it uses as much as digits as its factorization.

20821789 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 16128, while the sum is 37.

The square root of 20821789 is about 4563.0898522821. The cubic root of 20821789 is about 275.1097699521.

The spelling of 20821789 in words is "twenty million, eight hundred twenty-one thousand, seven hundred eighty-nine".