21405100 has 18 divisors (see below), whose sum is σ = 46449284. Its totient is φ = 8562000.

The previous prime is 21405067. The next prime is 21405113. The reversal of 21405100 is 150412.

21405100 is nontrivially palindromic in base 9.

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, 106926 + ... + 107125.

Almost surely, 2^21405100 is an apocalyptic number.

21405100 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21405100 is an abundant number, since it is smaller than the sum of its proper divisors (25044184).

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

21405100 is a wasteful number, since it uses less digits than its factorization.

21405100 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 214065 (or 214058 counting only the distinct ones).

The product of its (nonzero) digits is 40, while the sum is 13.

The square root of 21405100 is about 4626.5646002190. The cubic root of 21405100 is about 277.6551630694.

Adding to 21405100 its reverse (150412), we get a palindrome (21555512).

The spelling of 21405100 in words is "twenty-one million, four hundred five thousand, one hundred".