21129404 has 12 divisors (see below), whose sum is σ = 37674504. Its totient is φ = 10365264.

The previous prime is 21129403. The next prime is 21129439. The reversal of 21129404 is 40492112.

It is a self number, because there is not a number n which added to its sum of digits gives 21129404.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21129403) 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 3 ways as a sum of consecutive naturals, for example, 49622 + ... + 50045.

It is an arithmetic number, because the mean of its divisors is an integer number (3139542).

Almost surely, 2^21129404 is an apocalyptic number.

It is an amenable number.

21129404 is a deficient number, since it is larger than the sum of its proper divisors (16545100).

21129404 is a wasteful number, since it uses less digits than its factorization.

21129404 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 99724 (or 99722 counting only the distinct ones).

The product of its (nonzero) digits is 576, while the sum is 23.

The square root of 21129404 is about 4596.6731447863. The cubic root of 21129404 is about 276.4579493881.

The spelling of 21129404 in words is "twenty-one million, one hundred twenty-nine thousand, four hundred four".