21026987 has 2 divisors, whose sum is σ = 21026988. Its totient is φ = 21026986.

The previous prime is 21026983. The next prime is 21027007. The reversal of 21026987 is 78962012.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21026987 - 2² = 21026983 is a prime.

It is not a weakly prime, because it can be changed into another prime (21026983) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10513493 + 10513494.

It is an arithmetic number, because the mean of its divisors is an integer number (10513494).

Almost surely, 2^21026987 is an apocalyptic number.

21026987 is a deficient number, since it is larger than the sum of its proper divisors (1).

21026987 is an equidigital number, since it uses as much as digits as its factorization.

21026987 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 12096, while the sum is 35.

The square root of 21026987 is about 4585.5192726669. The cubic root of 21026987 is about 276.0105497263.

Adding to 21026987 its reverse (78962012), we get a palindrome (99988999).

The spelling of 21026987 in words is "twenty-one million, twenty-six thousand, nine hundred eighty-seven".