20418781 has 2 divisors, whose sum is σ = 20418782. Its totient is φ = 20418780.

The previous prime is 20418773. The next prime is 20418799. The reversal of 20418781 is 18781402.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 19624900 + 793881 = 4430^2 + 891^2 .

It is a cyclic number.

It is not a de Polignac number, because 20418781 - 2³ = 20418773 is a prime.

It is a super-2 number, since 2×20418781² = 833853235051922, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20418701) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10209390 + 10209391.

It is an arithmetic number, because the mean of its divisors is an integer number (10209391).

Almost surely, 2^20418781 is an apocalyptic number.

It is an amenable number.

20418781 is a deficient number, since it is larger than the sum of its proper divisors (1).

20418781 is an equidigital number, since it uses as much as digits as its factorization.

20418781 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 3584, while the sum is 31.

The square root of 20418781 is about 4518.7145295980. The cubic root of 20418781 is about 273.3232673602.

The spelling of 20418781 in words is "twenty million, four hundred eighteen thousand, seven hundred eighty-one".