19907681 has 2 divisors, whose sum is σ = 19907682. Its totient is φ = 19907680.

The previous prime is 19907669. The next prime is 19907683. The reversal of 19907681 is 18670991.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 10297681 + 9610000 = 3209^2 + 3100^2 .

It is a cyclic number.

It is not a de Polignac number, because 19907681 - 2²² = 15713377 is a prime.

It is a super-2 number, since 2×19907681² = 792631525595522, which contains 22 as substring.

Together with 19907683, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (19907683) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9953840 + 9953841.

It is an arithmetic number, because the mean of its divisors is an integer number (9953841).

Almost surely, 2^19907681 is an apocalyptic number.

It is an amenable number.

19907681 is a deficient number, since it is larger than the sum of its proper divisors (1).

19907681 is an equidigital number, since it uses as much as digits as its factorization.

19907681 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 27216, while the sum is 41.

The square root of 19907681 is about 4461.8024384771. The cubic root of 19907681 is about 271.0234635167.

The spelling of 19907681 in words is "nineteen million, nine hundred seven thousand, six hundred eighty-one".