21158487 has 48 divisors (see below), whose sum is σ = 37227840. Its totient is φ = 11321856.

The previous prime is 21158471. The next prime is 21158519. The reversal of 21158487 is 78485112.

21158487 is a `hidden beast` number, since 21 + 158 + 487 = 666.

It is not a de Polignac number, because 21158487 - 2⁴ = 21158471 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21158987) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 67443 + ... + 67755.

It is an arithmetic number, because the mean of its divisors is an integer number (775580).

Almost surely, 2^21158487 is an apocalyptic number.

21158487 is a deficient number, since it is larger than the sum of its proper divisors (16069353).

21158487 is a wasteful number, since it uses less digits than its factorization.

21158487 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 392 (or 389 counting only the distinct ones).

The product of its digits is 17920, while the sum is 36.

The square root of 21158487 is about 4599.8355405384. The cubic root of 21158487 is about 276.5847322738.

The spelling of 21158487 in words is "twenty-one million, one hundred fifty-eight thousand, four hundred eighty-seven".