215681891381 has 4 divisors (see below), whose sum is σ = 235289336064. Its totient is φ = 196074446700.

The previous prime is 215681891363. The next prime is 215681891419. The reversal of 215681891381 is 183198186512.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 215681891381 - 2¹⁴ = 215681874997 is a prime.

It is a super-2 number, since 2×215681891381² (a number of 23 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (215681891681) 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, 9803722325 + ... + 9803722346.

It is an arithmetic number, because the mean of its divisors is an integer number (58822334016).

Almost surely, 2^215681891381 is an apocalyptic number.

It is an amenable number.

215681891381 is a deficient number, since it is larger than the sum of its proper divisors (19607444683).

215681891381 is a wasteful number, since it uses less digits than its factorization.

215681891381 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 19607444682.

The product of its digits is 829440, while the sum is 53.

The spelling of 215681891381 in words is "two hundred fifteen billion, six hundred eighty-one million, eight hundred ninety-one thousand, three hundred eighty-one".