20780761 has 2 divisors, whose sum is σ = 20780762. Its totient is φ = 20780760.

The previous prime is 20780759. The next prime is 20780779. The reversal of 20780761 is 16708702.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 19193161 + 1587600 = 4381^2 + 1260^2 .

It is a cyclic number.

It is not a de Polignac number, because 20780761 - 2¹ = 20780759 is a prime.

Together with 20780759, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (20780731) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10390380 + 10390381.

It is an arithmetic number, because the mean of its divisors is an integer number (10390381).

Almost surely, 2^20780761 is an apocalyptic number.

It is an amenable number.

20780761 is a deficient number, since it is larger than the sum of its proper divisors (1).

20780761 is an equidigital number, since it uses as much as digits as its factorization.

20780761 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 4704, while the sum is 31.

The square root of 20780761 is about 4558.5919975361. The cubic root of 20780761 is about 274.9289557525.

The spelling of 20780761 in words is "twenty million, seven hundred eighty thousand, seven hundred sixty-one".