21545786 has 4 divisors (see below), whose sum is σ = 32318682. Its totient is φ = 10772892.

The previous prime is 21545773. The next prime is 21545789. The reversal of 21545786 is 68754512.

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., 11015761 + 10530025 = 3319^2 + 3245^2 .

It is not an unprimeable number, because it can be changed into a prime (21545789) by changing a digit.

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, 5386445 + ... + 5386448.

Almost surely, 2^21545786 is an apocalyptic number.

21545786 is a deficient number, since it is larger than the sum of its proper divisors (10772896).

21545786 is a wasteful number, since it uses less digits than its factorization.

21545786 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10772895.

The product of its digits is 67200, while the sum is 38.

The square root of 21545786 is about 4641.7438533379. The cubic root of 21545786 is about 278.2621356451.

The spelling of 21545786 in words is "twenty-one million, five hundred forty-five thousand, seven hundred eighty-six".