21605036 has 6 divisors (see below), whose sum is σ = 37808820. Its totient is φ = 10802516.

The previous prime is 21605009. The next prime is 21605039. The reversal of 21605036 is 63050612.

It is a super-2 number, since 2×21605036² = 933555161122592, which contains 22 as substring.

It is a plaindrome in base 16.

It is not an unprimeable number, because it can be changed into a prime (21605039) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2700626 + ... + 2700633.

It is an arithmetic number, because the mean of its divisors is an integer number (6301470).

Almost surely, 2^21605036 is an apocalyptic number.

It is an amenable number.

21605036 is a deficient number, since it is larger than the sum of its proper divisors (16203784).

21605036 is a wasteful number, since it uses less digits than its factorization.

21605036 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5401263 (or 5401261 counting only the distinct ones).

The product of its (nonzero) digits is 1080, while the sum is 23.

The square root of 21605036 is about 4648.1217712104. The cubic root of 21605036 is about 278.5169718918.

Adding to 21605036 its reverse (63050612), we get a palindrome (84655648).

The spelling of 21605036 in words is "twenty-one million, six hundred five thousand, thirty-six".