20447681 has 2 divisors, whose sum is σ = 20447682. Its totient is φ = 20447680.

The previous prime is 20447677. The next prime is 20447683. The reversal of 20447681 is 18674402.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 16483600 + 3964081 = 4060^2 + 1991^2 .

It is a cyclic number.

It is not a de Polignac number, because 20447681 - 2² = 20447677 is a prime.

It is a super-2 number, since 2×20447681² = 836215316555522, which contains 22 as substring.

It is a Sophie Germain prime.

Together with 20447683, it forms a pair of twin primes.

It is a Chen prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (20447683) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10223840 + 10223841.

It is an arithmetic number, because the mean of its divisors is an integer number (10223841).

Almost surely, 2^20447681 is an apocalyptic number.

It is an amenable number.

20447681 is a deficient number, since it is larger than the sum of its proper divisors (1).

20447681 is an equidigital number, since it uses as much as digits as its factorization.

20447681 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 10752, while the sum is 32.

The square root of 20447681 is about 4521.9112109815. The cubic root of 20447681 is about 273.4521571746.

The spelling of 20447681 in words is "twenty million, four hundred forty-seven thousand, six hundred eighty-one".