19989997 has 2 divisors, whose sum is σ = 19989998. Its totient is φ = 19989996.

The previous prime is 19989973. The next prime is 19990031. The reversal of 19989997 is 79998991.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 11115556 + 8874441 = 3334^2 + 2979^2 .

It is a cyclic number.

It is not a de Polignac number, because 19989997 - 2¹¹ = 19987949 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (19989917) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9994998 + 9994999.

It is an arithmetic number, because the mean of its divisors is an integer number (9994999).

Almost surely, 2^19989997 is an apocalyptic number.

It is an amenable number.

19989997 is a deficient number, since it is larger than the sum of its proper divisors (1).

19989997 is an equidigital number, since it uses as much as digits as its factorization.

19989997 is an evil number, because the sum of its binary digits is even.

The product of its digits is 3306744, while the sum is 61.

The square root of 19989997 is about 4471.0174457275. The cubic root of 19989997 is about 271.3965002471.

The spelling of 19989997 in words is "nineteen million, nine hundred eighty-nine thousand, nine hundred ninety-seven".