7866991 has 16 divisors (see below), whose sum is σ = 8876448. Its totient is φ = 6912000.

The previous prime is 7866973. The next prime is 7866997. The reversal of 7866991 is 1996687.

It is a 11-Lehmer number, since φ(7866991) divides (7866991-1)¹¹.

It is a cyclic number.

It is not a de Polignac number, because 7866991 - 2⁵ = 7866959 is a prime.

It is an Ulam number.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (7866997) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 77841 + ... + 77941.

It is an arithmetic number, because the mean of its divisors is an integer number (554778).

Almost surely, 2^7866991 is an apocalyptic number.

7866991 is a deficient number, since it is larger than the sum of its proper divisors (1009457).

7866991 is a wasteful number, since it uses less digits than its factorization.

7866991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 282.

The product of its digits is 163296, while the sum is 46.

The square root of 7866991 is about 2804.8156802186. The cubic root of 7866991 is about 198.8853914450.

It can be divided in two parts, 786 and 6991, that added together give a palindrome (7777).

The spelling of 7866991 in words is "seven million, eight hundred sixty-six thousand, nine hundred ninety-one".