21660536524618 has 4 divisors (see below), whose sum is σ = 32490804786930. Its totient is φ = 10830268262308.

The previous prime is 21660536524589. The next prime is 21660536524619. The reversal of 21660536524618 is 81642563506612.

It is a happy number.

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., 14424097580649 + 7236438943969 = 3797907^2 + 2690063^2 .

It is not an unprimeable number, because it can be changed into a prime (21660536524619) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5415134131153 + ... + 5415134131156.

Almost surely, 2^{21660536524618} is an apocalyptic number.

21660536524618 is a deficient number, since it is larger than the sum of its proper divisors (10830268262312).

21660536524618 is a wasteful number, since it uses less digits than its factorization.

21660536524618 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10830268262311.

The product of its (nonzero) digits is 12441600, while the sum is 55.

The spelling of 21660536524618 in words is "twenty-one trillion, six hundred sixty billion, five hundred thirty-six million, five hundred twenty-four thousand, six hundred eighteen".