21057187 has 8 divisors (see below), whose sum is σ = 22386960. Its totient is φ = 19749600.

The previous prime is 21057173. The next prime is 21057191. The reversal of 21057187 is 78175012.

It is a happy number.

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-21057187 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21057137) 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 7 ways as a sum of consecutive naturals, for example, 3568 + ... + 7405.

It is an arithmetic number, because the mean of its divisors is an integer number (2798370).

Almost surely, 2^21057187 is an apocalyptic number.

21057187 is a deficient number, since it is larger than the sum of its proper divisors (1329773).

21057187 is a wasteful number, since it uses less digits than its factorization.

21057187 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11093.

The product of its (nonzero) digits is 3920, while the sum is 31.

The square root of 21057187 is about 4588.8110660606. The cubic root of 21057187 is about 276.1426265213.

The spelling of 21057187 in words is "twenty-one million, fifty-seven thousand, one hundred eighty-seven".