21317100 has 72 divisors (see below), whose sum is σ = 70495488. Its totient is φ = 4872000.

The previous prime is 21317083. The next prime is 21317129. The reversal of 21317100 is 171312.

It is a Harshad number since it is a multiple of its sum of digits (15).

It is a self number, because there is not a number n which added to its sum of digits gives 21317100.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 2976 + ... + 7175.

It is an arithmetic number, because the mean of its divisors is an integer number (979104).

Almost surely, 2^21317100 is an apocalyptic number.

21317100 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21317100 is an abundant number, since it is smaller than the sum of its proper divisors (49178388).

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

21317100 is a wasteful number, since it uses less digits than its factorization.

21317100 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10175 (or 10168 counting only the distinct ones).

The product of its (nonzero) digits is 42, while the sum is 15.

The square root of 21317100 is about 4617.0445092072. The cubic root of 21317100 is about 277.2741446101.

Adding to 21317100 its reverse (171312), we get a palindrome (21488412).

The spelling of 21317100 in words is "twenty-one million, three hundred seventeen thousand, one hundred".