19901681 has 2 divisors, whose sum is σ = 19901682. Its totient is φ = 19901680.

The previous prime is 19901663. The next prime is 19901699. The reversal of 19901681 is 18610991.

It is a balanced prime because it is at equal distance from previous prime (19901663) and next prime (19901699).

It can be written as a sum of positive squares in only one way, i.e., 19439281 + 462400 = 4409^2 + 680^2 .

It is a cyclic number.

It is not a de Polignac number, because 19901681 - 2¹⁴ = 19885297 is a prime.

It is a super-2 number, since 2×19901681² = 792153813251522, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (19901641) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9950840 + 9950841.

It is an arithmetic number, because the mean of its divisors is an integer number (9950841).

Almost surely, 2^19901681 is an apocalyptic number.

It is an amenable number.

19901681 is a deficient number, since it is larger than the sum of its proper divisors (1).

19901681 is an equidigital number, since it uses as much as digits as its factorization.

19901681 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 3888, while the sum is 35.

The square root of 19901681 is about 4461.1300137970. The cubic root of 19901681 is about 270.9962327513.

The spelling of 19901681 in words is "nineteen million, nine hundred one thousand, six hundred eighty-one".