21506705505616 has 10 divisors (see below), whose sum is σ = 41669241917162. Its totient is φ = 10753352752800.

The previous prime is 21506705505611. The next prime is 21506705505673. The reversal of 21506705505616 is 61650550760512.

It is a happy number.

It can be written as a sum of positive squares in only one way, i.e., 21506369150016 + 336355600 = 4637496^2 + 18340^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 21506705505616.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21506705505611) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 672084547035 + ... + 672084547066.

Almost surely, 2^{21506705505616} is an apocalyptic number.

It is an amenable number.

21506705505616 is a deficient number, since it is larger than the sum of its proper divisors (20162536411546).

21506705505616 is a wasteful number, since it uses less digits than its factorization.

21506705505616 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1344169094109 (or 1344169094103 counting only the distinct ones).

The product of its (nonzero) digits is 1890000, while the sum is 49.

The spelling of 21506705505616 in words is "twenty-one trillion, five hundred six billion, seven hundred five million, five hundred five thousand, six hundred sixteen".