21651256 has 24 divisors (see below), whose sum is σ = 44624160. Its totient is φ = 9841040.

The previous prime is 21651221. The next prime is 21651271. The reversal of 21651256 is 65215612.

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 5 ways as a sum of consecutive naturals, for example, 10216 + ... + 12151.

It is an arithmetic number, because the mean of its divisors is an integer number (1859340).

Almost surely, 2^21651256 is an apocalyptic number.

It is an amenable number.

21651256 is an abundant number, since it is smaller than the sum of its proper divisors (22972904).

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

21651256 is a wasteful number, since it uses less digits than its factorization.

21651256 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 22395 (or 22380 counting only the distinct ones).

The product of its digits is 3600, while the sum is 28.

The square root of 21651256 is about 4653.0910156583. The cubic root of 21651256 is about 278.7154423701.

Adding to 21651256 its reverse (65215612), we get a palindrome (86866868).

The spelling of 21651256 in words is "twenty-one million, six hundred fifty-one thousand, two hundred fifty-six".