21587987 has 2 divisors, whose sum is σ = 21587988. Its totient is φ = 21587986.

The previous prime is 21587963. The next prime is 21588001. The reversal of 21587987 is 78978512.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21587987 - 2¹⁰ = 21586963 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21587887) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10793993 + 10793994.

It is an arithmetic number, because the mean of its divisors is an integer number (10793994).

Almost surely, 2^21587987 is an apocalyptic number.

21587987 is a deficient number, since it is larger than the sum of its proper divisors (1).

21587987 is an equidigital number, since it uses as much as digits as its factorization.

21587987 is an evil number, because the sum of its binary digits is even.

The product of its digits is 282240, while the sum is 47.

The square root of 21587987 is about 4646.2874426794. The cubic root of 21587987 is about 278.4436913623.

The spelling of 21587987 in words is "twenty-one million, five hundred eighty-seven thousand, nine hundred eighty-seven".