1377991 has 4 divisors (see below), whose sum is σ = 1415272. Its totient is φ = 1340712.

The previous prime is 1377983. The next prime is 1378001. The reversal of 1377991 is 1997731.

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 1377991 - 2³ = 1377983 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (37), and also a Moran number because the ratio is a prime number: 37243 = 1377991 / (1 + 3 + 7 + 7 + 9 + 9 + 1).

It is a Duffinian number.

1377991 is a lucky number.

It is a self number, because there is not a number n which added to its sum of digits gives 1377991.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1377911) 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, 18585 + ... + 18658.

It is an arithmetic number, because the mean of its divisors is an integer number (353818).

2^1377991 is an apocalyptic number.

1377991 is a deficient number, since it is larger than the sum of its proper divisors (37281).

1377991 is an equidigital number, since it uses as much as digits as its factorization.

1377991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 37280.

The product of its digits is 11907, while the sum is 37.

The square root of 1377991 is about 1173.8786138268. The cubic root of 1377991 is about 111.2795755227.

It can be divided in two parts, 137 and 7991, that added together give a triangular number (8128 = T₁₂₇).

The spelling of 1377991 in words is "one million, three hundred seventy-seven thousand, nine hundred ninety-one".