21257630 has 32 divisors (see below), whose sum is σ = 40366080. Its totient is φ = 8048160.

The previous prime is 21257581. The next prime is 21257651. The reversal of 21257630 is 3675212.

It is a self number, because there is not a number n which added to its sum of digits gives 21257630.

It is a congruent number.

It is an unprimeable number.

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 15 ways as a sum of consecutive naturals, for example, 13841 + ... + 15299.

It is an arithmetic number, because the mean of its divisors is an integer number (1261440).

Almost surely, 2^21257630 is an apocalyptic number.

21257630 is a deficient number, since it is larger than the sum of its proper divisors (19108450).

21257630 is a wasteful number, since it uses less digits than its factorization.

21257630 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1544.

The product of its (nonzero) digits is 2520, while the sum is 26.

The square root of 21257630 is about 4610.5997440680. The cubic root of 21257630 is about 277.0160599237.

The spelling of 21257630 in words is "twenty-one million, two hundred fifty-seven thousand, six hundred thirty".