21121804 has 24 divisors (see below), whose sum is σ = 40492368. Its totient is φ = 9560640.

The previous prime is 21121781. The next prime is 21121811. The reversal of 21121804 is 40812112.

It is a happy number.

It is a super-2 number, since 2×21121804² = 892261208428832, which contains 22 as substring.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 11322 + ... + 13054.

It is an arithmetic number, because the mean of its divisors is an integer number (1687182).

Almost surely, 2^21121804 is an apocalyptic number.

It is an amenable number.

21121804 is a deficient number, since it is larger than the sum of its proper divisors (19370564).

21121804 is a wasteful number, since it uses less digits than its factorization.

21121804 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2025 (or 2023 counting only the distinct ones).

The product of its (nonzero) digits is 128, while the sum is 19.

The square root of 21121804 is about 4595.8463855965. The cubic root of 21121804 is about 276.4247991806.

Adding to 21121804 its reverse (40812112), we get a palindrome (61933916).

It can be divided in two parts, 2112 and 1804, that added together give a triangular number (3916 = T₈₈).

The spelling of 21121804 in words is "twenty-one million, one hundred twenty-one thousand, eight hundred four".