20819797 has 2 divisors, whose sum is σ = 20819798. Its totient is φ = 20819796.

The previous prime is 20819791. The next prime is 20819809. The reversal of 20819797 is 79791802.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 17690436 + 3129361 = 4206^2 + 1769^2 .

It is a cyclic number.

It is not a de Polignac number, because 20819797 - 2¹⁵ = 20787029 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20819791) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10409898 + 10409899.

It is an arithmetic number, because the mean of its divisors is an integer number (10409899).

Almost surely, 2^20819797 is an apocalyptic number.

It is an amenable number.

20819797 is a deficient number, since it is larger than the sum of its proper divisors (1).

20819797 is an equidigital number, since it uses as much as digits as its factorization.

20819797 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 63504, while the sum is 43.

The square root of 20819797 is about 4562.8715739104. The cubic root of 20819797 is about 275.1009965123.

The spelling of 20819797 in words is "twenty million, eight hundred nineteen thousand, seven hundred ninety-seven".