20987489 has 2 divisors, whose sum is σ = 20987490. Its totient is φ = 20987488.

The previous prime is 20987479. The next prime is 20987513. The reversal of 20987489 is 98478902.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 17808400 + 3179089 = 4220^2 + 1783^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20987489 is a prime.

It is a super-3 number, since 3×20987489³ (a number of 23 digits) contains 333 as substring.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (20987429) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10493744 + 10493745.

It is an arithmetic number, because the mean of its divisors is an integer number (10493745).

Almost surely, 2^20987489 is an apocalyptic number.

It is an amenable number.

20987489 is a deficient number, since it is larger than the sum of its proper divisors (1).

20987489 is an equidigital number, since it uses as much as digits as its factorization.

20987489 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 290304, while the sum is 47.

The square root of 20987489 is about 4581.2104295699. The cubic root of 20987489 is about 275.8376180234.

The spelling of 20987489 in words is "twenty million, nine hundred eighty-seven thousand, four hundred eighty-nine".