20687489 has 2 divisors, whose sum is σ = 20687490. Its totient is φ = 20687488.

The previous prime is 20687467. The next prime is 20687497. The reversal of 20687489 is 98478602.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 19228225 + 1459264 = 4385^2 + 1208^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20687489 is a prime.

It is a super-2 number, since 2×20687489² = 855944402250242, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (20687449) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10343744 + 10343745.

It is an arithmetic number, because the mean of its divisors is an integer number (10343745).

Almost surely, 2^20687489 is an apocalyptic number.

It is an amenable number.

20687489 is a deficient number, since it is larger than the sum of its proper divisors (1).

20687489 is an equidigital number, since it uses as much as digits as its factorization.

20687489 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 193536, while the sum is 44.

The square root of 20687489 is about 4548.3501404355. The cubic root of 20687489 is about 274.5170100596.

The spelling of 20687489 in words is "twenty million, six hundred eighty-seven thousand, four hundred eighty-nine".