20040781 has 2 divisors, whose sum is σ = 20040782. Its totient is φ = 20040780.

The previous prime is 20040737. The next prime is 20040793. The reversal of 20040781 is 18704002.

20040781 = 3165² + 3166².

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 10023556 + 10017225 = 3166^2 + 3165^2 .

It is a cyclic number.

It is not a de Polignac number, because 20040781 - 2¹³ = 20032589 is a prime.

It is a super-2 number, since 2×20040781² = 803265806179922, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20040701) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10020390 + 10020391.

It is an arithmetic number, because the mean of its divisors is an integer number (10020391).

Almost surely, 2^20040781 is an apocalyptic number.

20040781 is the 3166-th centered square number.

It is an amenable number.

20040781 is a deficient number, since it is larger than the sum of its proper divisors (1).

20040781 is an equidigital number, since it uses as much as digits as its factorization.

20040781 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 448, while the sum is 22.

The square root of 20040781 is about 4476.6930875368. The cubic root of 20040781 is about 271.6261308449.

Adding to 20040781 its reverse (18704002), we get a palindrome (38744783).

The spelling of 20040781 in words is "twenty million, forty thousand, seven hundred eighty-one".