21091628 has 48 divisors (see below), whose sum is σ = 41023584. Its totient is φ = 9446400.

The previous prime is 21091607. The next prime is 21091633. The reversal of 21091628 is 82619012.

It is a self number, because there is not a number n which added to its sum of digits gives 21091628.

It is an unprimeable number.

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 15 ways as a sum of consecutive naturals, for example, 208778 + ... + 208878.

It is an arithmetic number, because the mean of its divisors is an integer number (854658).

Almost surely, 2^21091628 is an apocalyptic number.

It is an amenable number.

21091628 is a deficient number, since it is larger than the sum of its proper divisors (19931956).

21091628 is a wasteful number, since it uses less digits than its factorization.

21091628 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 242 (or 240 counting only the distinct ones).

The product of its (nonzero) digits is 1728, while the sum is 29.

The square root of 21091628 is about 4592.5622478090. The cubic root of 21091628 is about 276.2930968845.

The spelling of 21091628 in words is "twenty-one million, ninety-one thousand, six hundred twenty-eight".