21057418 has 4 divisors (see below), whose sum is σ = 31586130. Its totient is φ = 10528708.

The previous prime is 21057341. The next prime is 21057419. The reversal of 21057418 is 81475012.

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

It can be written as a sum of positive squares in only one way, i.e., 14691889 + 6365529 = 3833^2 + 2523^2 .

It is not an unprimeable number, because it can be changed into a prime (21057419) 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 as a sum of consecutive naturals, namely, 5264353 + ... + 5264356.

Almost surely, 2^21057418 is an apocalyptic number.

21057418 is a deficient number, since it is larger than the sum of its proper divisors (10528712).

21057418 is a wasteful number, since it uses less digits than its factorization.

21057418 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10528711.

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

The square root of 21057418 is about 4588.8362359099. The cubic root of 21057418 is about 276.1436362907.

The spelling of 21057418 in words is "twenty-one million, fifty-seven thousand, four hundred eighteen".