20787409 has 2 divisors, whose sum is σ = 20787410. Its totient is φ = 20787408.

The previous prime is 20787401. The next prime is 20787419. The reversal of 20787409 is 90478702.

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., 20729809 + 57600 = 4553^2 + 240^2 .

It is a cyclic number.

It is not a de Polignac number, because 20787409 - 2³ = 20787401 is a prime.

It is not a weakly prime, because it can be changed into another prime (20787401) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10393704 + 10393705.

It is an arithmetic number, because the mean of its divisors is an integer number (10393705).

Almost surely, 2^20787409 is an apocalyptic number.

It is an amenable number.

20787409 is a deficient number, since it is larger than the sum of its proper divisors (1).

20787409 is an equidigital number, since it uses as much as digits as its factorization.

20787409 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 28224, while the sum is 37.

The square root of 20787409 is about 4559.3211117446. The cubic root of 20787409 is about 274.9582702521.

It can be divided in two parts, 207 and 87409, that added together give a square (87616 = 296²).

The spelling of 20787409 in words is "twenty million, seven hundred eighty-seven thousand, four hundred nine".