280906991 has 4 divisors (see below), whose sum is σ = 281065800. Its totient is φ = 280748184.

The previous prime is 280906987. The next prime is 280906999. The reversal of 280906991 is 199609082.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 199609082 = 2 ⋅99804541.

It is a cyclic number.

It is not a de Polignac number, because 280906991 - 2² = 280906987 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 (280906999) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 76721 + ... + 80298.

It is an arithmetic number, because the mean of its divisors is an integer number (70266450).

Almost surely, 2^280906991 is an apocalyptic number.

280906991 is a deficient number, since it is larger than the sum of its proper divisors (158809).

280906991 is a wasteful number, since it uses less digits than its factorization.

280906991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 158808.

The product of its (nonzero) digits is 69984, while the sum is 44.

The square root of 280906991 is about 16760.2801587563. The cubic root of 280906991 is about 654.9188882331.

The spelling of 280906991 in words is "two hundred eighty million, nine hundred six thousand, nine hundred ninety-one".