21257100 has 72 divisors (see below), whose sum is σ = 68346320. Its totient is φ = 5667840.

The previous prime is 21257077. The next prime is 21257101. The reversal of 21257100 is 175212.

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21257101) by changing a digit.

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 23 ways as a sum of consecutive naturals, for example, 1237 + ... + 6636.

Almost surely, 2^21257100 is an apocalyptic number.

21257100 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21257100, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (34173160).

21257100 is an abundant number, since it is smaller than the sum of its proper divisors (47089220).

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

21257100 is a wasteful number, since it uses less digits than its factorization.

21257100 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7896 (or 7883 counting only the distinct ones).

The product of its (nonzero) digits is 140, while the sum is 18.

The square root of 21257100 is about 4610.5422674562. The cubic root of 21257100 is about 277.0137576957.

The spelling of 21257100 in words is "twenty-one million, two hundred fifty-seven thousand, one hundred".