21101256 has 128 divisors (see below), whose sum is σ = 65318400. Its totient is φ = 6258240.

The previous prime is 21101251. The next prime is 21101257. The reversal of 21101256 is 65210112.

It is a Harshad number since it is a multiple of its sum of digits (18).

It is not an unprimeable number, because it can be changed into a prime (21101251) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 197155 + ... + 197261.

It is an arithmetic number, because the mean of its divisors is an integer number (510300).

Almost surely, 2^21101256 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21101256, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (32659200).

21101256 is an abundant number, since it is smaller than the sum of its proper divisors (44217144).

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

21101256 is a wasteful number, since it uses less digits than its factorization.

21101256 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 216 (or 206 counting only the distinct ones).

The product of its (nonzero) digits is 120, while the sum is 18.

The square root of 21101256 is about 4593.6103448159. The cubic root of 21101256 is about 276.3351316557.

Adding to 21101256 its reverse (65210112), we get a palindrome (86311368).

The spelling of 21101256 in words is "twenty-one million, one hundred one thousand, two hundred fifty-six".