21007087 has 4 divisors (see below), whose sum is σ = 22242816. Its totient is φ = 19771360.

The previous prime is 21007069. The next prime is 21007099. The reversal of 21007087 is 78070012.

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 21007087 - 2⁷ = 21006959 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 (21007067) 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, 617839 + ... + 617872.

It is an arithmetic number, because the mean of its divisors is an integer number (5560704).

Almost surely, 2^21007087 is an apocalyptic number.

21007087 is a deficient number, since it is larger than the sum of its proper divisors (1235729).

21007087 is a wasteful number, since it uses less digits than its factorization.

21007087 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1235728.

The product of its (nonzero) digits is 784, while the sum is 25.

The square root of 21007087 is about 4583.3488848221. The cubic root of 21007087 is about 275.9234498549.

Adding to 21007087 its reverse (78070012), we get a palindrome (99077099).

The spelling of 21007087 in words is "twenty-one million, seven thousand, eighty-seven".