20521987 has 2 divisors, whose sum is σ = 20521988. Its totient is φ = 20521986.

The previous prime is 20521981. The next prime is 20522023. The reversal of 20521987 is 78912502.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 20521987 - 2⁷ = 20521859 is a prime.

It is not a weakly prime, because it can be changed into another prime (20521981) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10260993 + 10260994.

It is an arithmetic number, because the mean of its divisors is an integer number (10260994).

Almost surely, 2^20521987 is an apocalyptic number.

20521987 is a deficient number, since it is larger than the sum of its proper divisors (1).

20521987 is an equidigital number, since it uses as much as digits as its factorization.

20521987 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 10080, while the sum is 34.

The square root of 20521987 is about 4530.1199763362. The cubic root of 20521987 is about 273.7829945705.

The spelling of 20521987 in words is "twenty million, five hundred twenty-one thousand, nine hundred eighty-seven".