21080987 has 2 divisors, whose sum is σ = 21080988. Its totient is φ = 21080986.

The previous prime is 21080977. The next prime is 21081017. The reversal of 21080987 is 78908012.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21080987 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21080977) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10540493 + 10540494.

It is an arithmetic number, because the mean of its divisors is an integer number (10540494).

Almost surely, 2^21080987 is an apocalyptic number.

21080987 is a deficient number, since it is larger than the sum of its proper divisors (1).

21080987 is an equidigital number, since it uses as much as digits as its factorization.

21080987 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 8064, while the sum is 35.

The square root of 21080987 is about 4591.4035980297. The cubic root of 21080987 is about 276.2466245842.

Adding to 21080987 its reverse (78908012), we get a palindrome (99988999).

The spelling of 21080987 in words is "twenty-one million, eighty thousand, nine hundred eighty-seven".