21172011516 has 36 divisors (see below), whose sum is σ = 54395492424. Its totient is φ = 6941642400.

The previous prime is 21172011473. The next prime is 21172011533. The reversal of 21172011516 is 61511027112.

21172011516 is a `hidden beast` number, since 2 + 117 + 20 + 11 + 516 = 666.

It is a tau number, because it is divible by the number of its divisors (36).

It is a self number, because there is not a number n which added to its sum of digits gives 21172011516.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 4818390 + ... + 4822781.

Almost surely, 2^21172011516 is an apocalyptic number.

It is an amenable number.

21172011516 is an abundant number, since it is smaller than the sum of its proper divisors (33223480908).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21172011516 is a wasteful number, since it uses less digits than its factorization.

21172011516 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9641242 (or 9641237 counting only the distinct ones).

The product of its (nonzero) digits is 840, while the sum is 27.

Adding to 21172011516 its reverse (61511027112), we get a palindrome (82683038628).

The spelling of 21172011516 in words is "twenty-one billion, one hundred seventy-two million, eleven thousand, five hundred sixteen".