21042787 has 8 divisors (see below), whose sum is σ = 22334832. Its totient is φ = 19756800.

The previous prime is 21042739. The next prime is 21042803. The reversal of 21042787 is 78724012.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21042787 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21042737) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 7087 + ... + 9607.

It is an arithmetic number, because the mean of its divisors is an integer number (2791854).

Almost surely, 2^21042787 is an apocalyptic number.

21042787 is a deficient number, since it is larger than the sum of its proper divisors (1292045).

21042787 is a wasteful number, since it uses less digits than its factorization.

21042787 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3029.

The product of its (nonzero) digits is 6272, while the sum is 31.

The square root of 21042787 is about 4587.2417638489. The cubic root of 21042787 is about 276.0796652688.

Adding to 21042787 its reverse (78724012), we get a palindrome (99766799).

The spelling of 21042787 in words is "twenty-one million, forty-two thousand, seven hundred eighty-seven".