19921997 has 2 divisors, whose sum is σ = 19921998. Its totient is φ = 19921996.

The previous prime is 19921991. The next prime is 19922033. The reversal of 19921997 is 79912991.

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., 17522596 + 2399401 = 4186^2 + 1549^2 .

It is a cyclic number.

It is not a de Polignac number, because 19921997 - 2¹⁰ = 19920973 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (19921991) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9960998 + 9960999.

It is an arithmetic number, because the mean of its divisors is an integer number (9960999).

Almost surely, 2^19921997 is an apocalyptic number.

It is an amenable number.

19921997 is a deficient number, since it is larger than the sum of its proper divisors (1).

19921997 is an equidigital number, since it uses as much as digits as its factorization.

19921997 is an evil number, because the sum of its binary digits is even.

The product of its digits is 91854, while the sum is 47.

The square root of 19921997 is about 4463.4064345520. The cubic root of 19921997 is about 271.0884140287.

The spelling of 19921997 in words is "nineteen million, nine hundred twenty-one thousand, nine hundred ninety-seven".