21010987 has 2 divisors, whose sum is σ = 21010988. Its totient is φ = 21010986.

The previous prime is 21010973. The next prime is 21011009. The reversal of 21010987 is 78901012.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21010987 - 2⁷ = 21010859 is a prime.

It is an alternating number because its digits alternate between even and odd.

It is not a weakly prime, because it can be changed into another prime (21010967) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10505493 + 10505494.

It is an arithmetic number, because the mean of its divisors is an integer number (10505494).

Almost surely, 2^21010987 is an apocalyptic number.

21010987 is a deficient number, since it is larger than the sum of its proper divisors (1).

21010987 is an equidigital number, since it uses as much as digits as its factorization.

21010987 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1008, while the sum is 28.

The square root of 21010987 is about 4583.7743181793. The cubic root of 21010987 is about 275.9405240113.

Adding to 21010987 its reverse (78901012), we get a palindrome (99911999).

The spelling of 21010987 in words is "twenty-one million, ten thousand, nine hundred eighty-seven".