378999991 has 4 divisors (see below), whose sum is σ = 389243272. Its totient is φ = 368756712.

The previous prime is 378999967. The next prime is 378999997. The reversal of 378999991 is 199999873.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 199999873 = 887 ⋅225479.

It is a cyclic number.

It is not a de Polignac number, because 378999991 - 2¹¹ = 378997943 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (378999997) 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, 5121585 + ... + 5121658.

It is an arithmetic number, because the mean of its divisors is an integer number (97310818).

Almost surely, 2^378999991 is an apocalyptic number.

378999991 is a deficient number, since it is larger than the sum of its proper divisors (10243281).

378999991 is a wasteful number, since it uses less digits than its factorization.

378999991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10243280.

The product of its digits is 9920232, while the sum is 64.

The square root of 378999991 is about 19467.9221027823. The cubic root of 378999991 is about 723.6797158619.

The spelling of 378999991 in words is "three hundred seventy-eight million, nine hundred ninety-nine thousand, nine hundred ninety-one".