20801681 has 2 divisors, whose sum is σ = 20801682. Its totient is φ = 20801680.

The previous prime is 20801647. The next prime is 20801699. The reversal of 20801681 is 18610802.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 18190225 + 2611456 = 4265^2 + 1616^2 .

It is a cyclic number.

It is not a de Polignac number, because 20801681 - 2⁶ = 20801617 is a prime.

It is a super-2 number, since 2×20801681² = 865419864851522, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 20801681.

It is not a weakly prime, because it can be changed into another prime (20804681) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10400840 + 10400841.

It is an arithmetic number, because the mean of its divisors is an integer number (10400841).

Almost surely, 2^20801681 is an apocalyptic number.

It is an amenable number.

20801681 is a deficient number, since it is larger than the sum of its proper divisors (1).

20801681 is an equidigital number, since it uses as much as digits as its factorization.

20801681 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 768, while the sum is 26.

The square root of 20801681 is about 4560.8859884895. The cubic root of 20801681 is about 275.0211818395.

The spelling of 20801681 in words is "twenty million, eight hundred one thousand, six hundred eighty-one".