21155604 has 24 divisors (see below), whose sum is σ = 49476000. Its totient is φ = 7035744.

The previous prime is 21155591. The next prime is 21155611. The reversal of 21155604 is 40655112.

It is a congruent number.

It is an unprimeable number.

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 7 ways as a sum of consecutive naturals, for example, 4222 + ... + 7754.

It is an arithmetic number, because the mean of its divisors is an integer number (2061500).

Almost surely, 2^21155604 is an apocalyptic number.

It is an amenable number.

21155604 is an abundant number, since it is smaller than the sum of its proper divisors (28320396).

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

21155604 is a wasteful number, since it uses less digits than its factorization.

21155604 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4039 (or 4037 counting only the distinct ones).

The product of its (nonzero) digits is 1200, while the sum is 24.

The square root of 21155604 is about 4599.5221490933. The cubic root of 21155604 is about 276.5721694663.

The spelling of 21155604 in words is "twenty-one million, one hundred fifty-five thousand, six hundred four".