21299987 has 2 divisors, whose sum is σ = 21299988. Its totient is φ = 21299986.

The previous prime is 21299983. The next prime is 21300029. The reversal of 21299987 is 78999212.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21299987 - 2² = 21299983 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21299983) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10649993 + 10649994.

It is an arithmetic number, because the mean of its divisors is an integer number (10649994).

Almost surely, 2^21299987 is an apocalyptic number.

21299987 is a deficient number, since it is larger than the sum of its proper divisors (1).

21299987 is an equidigital number, since it uses as much as digits as its factorization.

21299987 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 163296, while the sum is 47.

The square root of 21299987 is about 4615.1908952935. The cubic root of 21299987 is about 277.1999277805.

The spelling of 21299987 in words is "twenty-one million, two hundred ninety-nine thousand, nine hundred eighty-seven".