21809036 has 24 divisors (see below), whose sum is σ = 40783680. Its totient is φ = 10174032.

The previous prime is 21809009. The next prime is 21809057. The reversal of 21809036 is 63090812.

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, 2951 + ... + 7233.

It is an arithmetic number, because the mean of its divisors is an integer number (1699320).

Almost surely, 2^21809036 is an apocalyptic number.

It is an amenable number.

21809036 is a deficient number, since it is larger than the sum of its proper divisors (18974644).

21809036 is a wasteful number, since it uses less digits than its factorization.

21809036 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4373 (or 4371 counting only the distinct ones).

The product of its (nonzero) digits is 2592, while the sum is 29.

The square root of 21809036 is about 4670.0145610051. The cubic root of 21809036 is about 279.3908355345.

Adding to 21809036 its reverse (63090812), we get a palindrome (84899848).

The spelling of 21809036 in words is "twenty-one million, eight hundred nine thousand, thirty-six".