21636506 has 4 divisors (see below), whose sum is σ = 32454762. Its totient is φ = 10818252.

The previous prime is 21636499. The next prime is 21636521. The reversal of 21636506 is 60563612.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in only one way, i.e., 12666481 + 8970025 = 3559^2 + 2995^2 .

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 as a sum of consecutive naturals, namely, 5409125 + ... + 5409128.

Almost surely, 2^21636506 is an apocalyptic number.

21636506 is a deficient number, since it is larger than the sum of its proper divisors (10818256).

21636506 is a wasteful number, since it uses less digits than its factorization.

21636506 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10818255.

The product of its (nonzero) digits is 6480, while the sum is 29.

The square root of 21636506 is about 4651.5057777025. The cubic root of 21636506 is about 278.6521360091.

The spelling of 21636506 in words is "twenty-one million, six hundred thirty-six thousand, five hundred six".