20740781 has 2 divisors, whose sum is σ = 20740782. Its totient is φ = 20740780.

The previous prime is 20740777. The next prime is 20740789. The reversal of 20740781 is 18704702.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 12709225 + 8031556 = 3565^2 + 2834^2 .

It is a cyclic number.

It is not a de Polignac number, because 20740781 - 2² = 20740777 is a prime.

It is a super-3 number, since 3×20740781³ (a number of 23 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20740789) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10370390 + 10370391.

It is an arithmetic number, because the mean of its divisors is an integer number (10370391).

Almost surely, 2^20740781 is an apocalyptic number.

It is an amenable number.

20740781 is a deficient number, since it is larger than the sum of its proper divisors (1).

20740781 is an equidigital number, since it uses as much as digits as its factorization.

20740781 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 3136, while the sum is 29.

The square root of 20740781 is about 4554.2047604384. The cubic root of 20740781 is about 274.7525310918.

The spelling of 20740781 in words is "twenty million, seven hundred forty thousand, seven hundred eighty-one".