20971987 has 2 divisors, whose sum is σ = 20971988. Its totient is φ = 20971986.

The previous prime is 20971969. The next prime is 20971997. The reversal of 20971987 is 78917902.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 20971987 - 2¹⁹ = 20447699 is a prime.

It is not a weakly prime, because it can be changed into another prime (20971957) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10485993 + 10485994.

It is an arithmetic number, because the mean of its divisors is an integer number (10485994).

Almost surely, 2^20971987 is an apocalyptic number.

20971987 is a deficient number, since it is larger than the sum of its proper divisors (1).

20971987 is an equidigital number, since it uses as much as digits as its factorization.

20971987 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 63504, while the sum is 43.

The square root of 20971987 is about 4579.5182060999. The cubic root of 20971987 is about 275.7696872673.

The spelling of 20971987 in words is "twenty million, nine hundred seventy-one thousand, nine hundred eighty-seven".