27991951 has 4 divisors (see below), whose sum is σ = 30145192. Its totient is φ = 25838712.

The previous prime is 27991939. The next prime is 27991967. The reversal of 27991951 is 15919972.

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 27991951 - 2¹¹ = 27989903 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 27991898 and 27991907.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (27991981) 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, 1076601 + ... + 1076626.

It is an arithmetic number, because the mean of its divisors is an integer number (7536298).

Almost surely, 2^27991951 is an apocalyptic number.

27991951 is a deficient number, since it is larger than the sum of its proper divisors (2153241).

27991951 is a wasteful number, since it uses less digits than its factorization.

27991951 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2153240.

The product of its digits is 51030, while the sum is 43.

The square root of 27991951 is about 5290.7420084521. The cubic root of 27991951 is about 303.6297973697.

The spelling of 27991951 in words is "twenty-seven million, nine hundred ninety-one thousand, nine hundred fifty-one".