981491781 has 4 divisors (see below), whose sum is σ = 1308655712. Its totient is φ = 654327852.

The previous prime is 981491779. The next prime is 981491783. The reversal of 981491781 is 187194189.

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 an interprime number because it is at equal distance from previous prime (981491779) and next prime (981491783).

It is not a de Polignac number, because 981491781 - 2¹ = 981491779 is a prime.

It is a super-2 number, since 2×981491781² = 1926652232341103922, which contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 981491781.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (981491783) 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, 163581961 + ... + 163581966.

It is an arithmetic number, because the mean of its divisors is an integer number (327163928).

Almost surely, 2^981491781 is an apocalyptic number.

It is an amenable number.

981491781 is a deficient number, since it is larger than the sum of its proper divisors (327163931).

981491781 is a wasteful number, since it uses less digits than its factorization.

981491781 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 327163930.

The product of its digits is 145152, while the sum is 48.

The square root of 981491781 is about 31328.7692225533. The cubic root of 981491781 is about 993.7921358345.

The spelling of 981491781 in words is "nine hundred eighty-one million, four hundred ninety-one thousand, seven hundred eighty-one".