21165559371 has 96 divisors (see below), whose sum is σ = 35678522880. Its totient is φ = 11956377600.

The previous prime is 21165559369. The next prime is 21165559417. The reversal of 21165559371 is 17395556112.

21165559371 is a `hidden beast` number, since 2 + 1 + 1 + 6 + 55 + 593 + 7 + 1 = 666.

It is not a de Polignac number, because 21165559371 - 2¹ = 21165559369 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21165559321) by changing a digit.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 56743941 + ... + 56744313.

It is an arithmetic number, because the mean of its divisors is an integer number (371651280).

Almost surely, 2^21165559371 is an apocalyptic number.

21165559371 is a deficient number, since it is larger than the sum of its proper divisors (14512963509).

21165559371 is a wasteful number, since it uses less digits than its factorization.

21165559371 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 817 (or 814 counting only the distinct ones).

The product of its digits is 283500, while the sum is 45.

The spelling of 21165559371 in words is "twenty-one billion, one hundred sixty-five million, five hundred fifty-nine thousand, three hundred seventy-one".