21645036 has 48 divisors (see below), whose sum is σ = 64135680. Its totient is φ = 6184080.

The previous prime is 21645023. The next prime is 21645053. The reversal of 21645036 is 63054612.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 13560 + ... + 15071.

It is an arithmetic number, because the mean of its divisors is an integer number (1336160).

Almost surely, 2^21645036 is an apocalyptic number.

It is an amenable number.

21645036 is an abundant number, since it is smaller than the sum of its proper divisors (42490644).

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

21645036 is a wasteful number, since it uses less digits than its factorization.

21645036 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 28651 (or 28643 counting only the distinct ones).

The product of its (nonzero) digits is 4320, while the sum is 27.

The square root of 21645036 is about 4652.4225947349. The cubic root of 21645036 is about 278.6887499065.

Adding to 21645036 its reverse (63054612), we get a palindrome (84699648).

The spelling of 21645036 in words is "twenty-one million, six hundred forty-five thousand, thirty-six".