990781 has 4 divisors (see below), whose sum is σ = 1080864. Its totient is φ = 900700.

The previous prime is 990767. The next prime is 990797. The reversal of 990781 is 187099.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 990781 - 2¹¹ = 988733 is a prime.

It is a super-2 number, since 2×990781² = 1963293979922, which contains 22 as substring.

It is an Ulam number.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (990761) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 45025 + ... + 45046.

It is an arithmetic number, because the mean of its divisors is an integer number (270216).

2⁹⁹⁰⁷⁸¹ is an apocalyptic number.

It is an amenable number.

990781 is a deficient number, since it is larger than the sum of its proper divisors (90083).

990781 is a wasteful number, since it uses less digits than its factorization.

990781 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 90082.

The product of its (nonzero) digits is 4536, while the sum is 34.

The square root of 990781 is about 995.3798270007. The cubic root of 990781 is about 99.6917508006.

It can be divided in two parts, 990 and 781, that added together give a palindrome (1771).

The spelling of 990781 in words is "nine hundred ninety thousand, seven hundred eighty-one".