21007387 has 4 divisors (see below), whose sum is σ = 21224056. Its totient is φ = 20790720.

The previous prime is 21007321. The next prime is 21007423. The reversal of 21007387 is 78370012.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21007387 - 2¹¹ = 21005339 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21007307) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 108189 + ... + 108382.

It is an arithmetic number, because the mean of its divisors is an integer number (5306014).

Almost surely, 2^21007387 is an apocalyptic number.

21007387 is a deficient number, since it is larger than the sum of its proper divisors (216669).

21007387 is an equidigital number, since it uses as much as digits as its factorization.

21007387 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 216668.

The product of its (nonzero) digits is 2352, while the sum is 28.

The square root of 21007387 is about 4583.3816118669. The cubic root of 21007387 is about 275.9247633265.

Adding to 21007387 its reverse (78370012), we get a palindrome (99377399).

The spelling of 21007387 in words is "twenty-one million, seven thousand, three hundred eighty-seven".