19720681 has 6 divisors (see below), whose sum is σ = 20378346. Its totient is φ = 19083600.

The previous prime is 19720669. The next prime is 19720699. The reversal of 19720681 is 18602791.

It is a happy number.

It can be written as a sum of positive squares in only one way, i.e., 17774656 + 1946025 = 4216^2 + 1395^2 .

It is not a de Polignac number, because 19720681 - 2¹⁹ = 19196393 is a prime.

It is a super-2 number, since 2×19720681² = 777810518207522, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (19720601) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 9300 + ... + 11221.

It is an arithmetic number, because the mean of its divisors is an integer number (3396391).

Almost surely, 2^19720681 is an apocalyptic number.

It is an amenable number.

19720681 is a deficient number, since it is larger than the sum of its proper divisors (657665).

19720681 is an equidigital number, since it uses as much as digits as its factorization.

19720681 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 20583 (or 20552 counting only the distinct ones).

The product of its (nonzero) digits is 6048, while the sum is 34.

The square root of 19720681 is about 4440.7973383166. The cubic root of 19720681 is about 270.1721855516.

The spelling of 19720681 in words is "nineteen million, seven hundred twenty thousand, six hundred eighty-one".