21275951616 has 320 divisors, whose sum is σ = 66133267200. Its totient is φ = 6744342528.

The previous prime is 21275951581. The next prime is 21275951659. The reversal of 21275951616 is 61615957212.

It is a happy number.

21275951616 is a `hidden beast` number, since 2 + 1 + 27 + 5 + 9 + 5 + 1 + 616 = 666.

It is a super-2 number, since 2×21275951616² (a number of 21 digits) contains 22 as substring.

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 in 31 ways as a sum of consecutive naturals, for example, 29265045 + ... + 29265771.

It is an arithmetic number, because the mean of its divisors is an integer number (206666460).

Almost surely, 2^21275951616 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21275951616, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (33066633600).

21275951616 is an abundant number, since it is smaller than the sum of its proper divisors (44857315584).

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

21275951616 is an equidigital number, since it uses as much as digits as its factorization.

21275951616 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 856 (or 834 counting only the distinct ones).

The product of its digits is 226800, while the sum is 45.

The spelling of 21275951616 in words is "twenty-one billion, two hundred seventy-five million, nine hundred fifty-one thousand, six hundred sixteen".