21299687 has 2 divisors, whose sum is σ = 21299688. Its totient is φ = 21299686.

The previous prime is 21299669. The next prime is 21299701. The reversal of 21299687 is 78699212.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21299687 - 2¹² = 21295591 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21299647) 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, 10649843 + 10649844.

It is an arithmetic number, because the mean of its divisors is an integer number (10649844).

Almost surely, 2^21299687 is an apocalyptic number.

21299687 is a deficient number, since it is larger than the sum of its proper divisors (1).

21299687 is an equidigital number, since it uses as much as digits as its factorization.

21299687 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 108864, while the sum is 44.

The square root of 21299687 is about 4615.1583938149. The cubic root of 21299687 is about 277.1986263655.

It can be divided in two parts, 212 and 99687, that added together give a palindrome (99899).

The spelling of 21299687 in words is "twenty-one million, two hundred ninety-nine thousand, six hundred eighty-seven".