391887268081 has 3 divisors (see below), whose sum is σ = 391887894091. Its totient is φ = 391886642072.

The previous prime is 391887267983. The next prime is 391887268109. The reversal of 391887268081 is 180862788193.

The square root of 391887268081 is 626009.

It is a perfect power (a square), and thus also a powerful number.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 180862788193 = 73 ⋅2477572441.

It can be written as a sum of positive squares in only one way, i.e., 32558954481 + 359328313600 = 180441^2 + 599440^2 .

It is not a de Polignac number, because 391887268081 - 2⁷ = 391887267953 is a prime.

It is a super-2 number, since 2×391887268081² (a number of 24 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (391887268481) by changing a digit.

It is a polite number, since it can be written in 2 ways as a sum of consecutive naturals, for example, 313005 + ... + 939013.

Almost surely, 2^391887268081 is an apocalyptic number.

391887268081 is the 626009-th square number.

391887268081 is the 313005-th centered octagonal number.

It is an amenable number.

391887268081 is a deficient number, since it is larger than the sum of its proper divisors (626010).

391887268081 is an frugal number, since it uses more digits than its factorization.

391887268081 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1252018 (or 626009 counting only the distinct ones).

The product of its (nonzero) digits is 9289728, while the sum is 61.

The spelling of 391887268081 in words is "three hundred ninety-one billion, eight hundred eighty-seven million, two hundred sixty-eight thousand, eighty-one".