781998 has 32 divisors (see below), whose sum is σ = 1833216. Its totient is φ = 217728.

The previous prime is 781997. The next prime is 781999. The reversal of 781998 is 899187.

It is an interprime number because it is at equal distance from previous prime (781997) and next prime (781999).

It is a super-2 number, since 2×781998² = 1223041744008, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (42).

It is an Ulam number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (781997) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1590 + ... + 2022.

It is an arithmetic number, because the mean of its divisors is an integer number (57288).

2⁷⁸¹⁹⁹⁸ is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 781998, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (916608).

781998 is an abundant number, since it is smaller than the sum of its proper divisors (1051218).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

781998 is a wasteful number, since it uses less digits than its factorization.

781998 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 488.

The product of its digits is 36288, while the sum is 42.

The square root of 781998 is about 884.3065079485. The cubic root of 781998 is about 92.1301717494.

The spelling of 781998 in words is "seven hundred eighty-one thousand, nine hundred ninety-eight".