21152287 has 4 divisors (see below), whose sum is σ = 22779400. Its totient is φ = 19525176.

The previous prime is 21152239. The next prime is 21152291. The reversal of 21152287 is 78225112.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21152287 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21152207) 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 in 3 ways as a sum of consecutive naturals, for example, 813537 + ... + 813562.

It is an arithmetic number, because the mean of its divisors is an integer number (5694850).

Almost surely, 2^21152287 is an apocalyptic number.

21152287 is a deficient number, since it is larger than the sum of its proper divisors (1627113).

21152287 is a wasteful number, since it uses less digits than its factorization.

21152287 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1627112.

The product of its digits is 2240, while the sum is 28.

The square root of 21152287 is about 4599.1615540226. The cubic root of 21152287 is about 276.5577140713.

Adding to 21152287 its reverse (78225112), we get a palindrome (99377399).

The spelling of 21152287 in words is "twenty-one million, one hundred fifty-two thousand, two hundred eighty-seven".