216990971871 has 4 divisors (see below), whose sum is σ = 289321295832. Its totient is φ = 144660647912.

The previous prime is 216990971861. The next prime is 216990971887. The reversal of 216990971871 is 178179099612.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 216990971871 - 2²¹ = 216988874719 is a prime.

It is a super-2 number, since 2×216990971871² (a number of 23 digits) contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (216990971801) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 36165161976 + ... + 36165161981.

It is an arithmetic number, because the mean of its divisors is an integer number (72330323958).

Almost surely, 2^216990971871 is an apocalyptic number.

216990971871 is a deficient number, since it is larger than the sum of its proper divisors (72330323961).

216990971871 is an equidigital number, since it uses as much as digits as its factorization.

216990971871 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 72330323960.

The product of its (nonzero) digits is 3429216, while the sum is 60.

The spelling of 216990971871 in words is "two hundred sixteen billion, nine hundred ninety million, nine hundred seventy-one thousand, eight hundred seventy-one".