21257910 has 64 divisors (see below), whose sum is σ = 58037760. Its totient is φ = 5533920.

The previous prime is 21257893. The next prime is 21257923. The reversal of 21257910 is 1975212.

It is a Harshad number since it is a multiple of its sum of digits (27).

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 31 ways as a sum of consecutive naturals, for example, 10695 + ... + 12525.

It is an arithmetic number, because the mean of its divisors is an integer number (906840).

Almost surely, 2^21257910 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21257910, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (29018880).

21257910 is an abundant number, since it is smaller than the sum of its proper divisors (36779850).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21257910 is a wasteful number, since it uses less digits than its factorization.

21257910 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1890 (or 1884 counting only the distinct ones).

The product of its (nonzero) digits is 1260, while the sum is 27.

The square root of 21257910 is about 4610.6301087812. The cubic root of 21257910 is about 277.0172761797.

The spelling of 21257910 in words is "twenty-one million, two hundred fifty-seven thousand, nine hundred ten".