27991440 has 80 divisors (see below), whose sum is σ = 96422400. Its totient is φ = 7463808.

The previous prime is 27991399. The next prime is 27991477. The reversal of 27991440 is 4419972.

It is a tau number, because it is divible by the number of its divisors (80).

It is a hoax number, since the sum of its digits (36) coincides with the sum of the digits of its distinct prime factors.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a junction number, because it is equal to n+sod(n) for n = 27991395 and 27991404.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 4320 + ... + 8639.

It is an arithmetic number, because the mean of its divisors is an integer number (1205280).

Almost surely, 2^27991440 is an apocalyptic number.

27991440 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

27991440 is the 4320-th pentagonal number.

It is an amenable number.

27991440 is an abundant number, since it is smaller than the sum of its proper divisors (68430960).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

27991440 is a wasteful number, since it uses less digits than its factorization.

27991440 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12981 (or 12969 counting only the distinct ones).

The product of its (nonzero) digits is 18144, while the sum is 36.

The square root of 27991440 is about 5290.6937163287. The cubic root of 27991440 is about 303.6279497460.

It can be divided in two parts, 279 and 91440, that added together give a palindrome (91719).

The spelling of 27991440 in words is "twenty-seven million, nine hundred ninety-one thousand, four hundred forty".