21608987 has 2 divisors, whose sum is σ = 21608988. Its totient is φ = 21608986.

The previous prime is 21608969. The next prime is 21609011. The reversal of 21608987 is 78980612.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21608987 - 2¹⁶ = 21543451 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21608957) 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, 10804493 + 10804494.

It is an arithmetic number, because the mean of its divisors is an integer number (10804494).

Almost surely, 2^21608987 is an apocalyptic number.

21608987 is a deficient number, since it is larger than the sum of its proper divisors (1).

21608987 is an equidigital number, since it uses as much as digits as its factorization.

21608987 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 48384, while the sum is 41.

The square root of 21608987 is about 4648.5467621613. The cubic root of 21608987 is about 278.5339486973.

The spelling of 21608987 in words is "twenty-one million, six hundred eight thousand, nine hundred eighty-seven".