1981390 has 8 divisors (see below), whose sum is σ = 3566520. Its totient is φ = 792552.

The previous prime is 1981361. The next prime is 1981393. The reversal of 1981390 is 931891.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a super-3 number, since 3×1981390³ = 23336254642078857000, which contains 333 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1981393) 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, 99060 + ... + 99079.

It is an arithmetic number, because the mean of its divisors is an integer number (445815).

2^1981390 is an apocalyptic number.

1981390 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

1981390 is a deficient number, since it is larger than the sum of its proper divisors (1585130).

1981390 is a wasteful number, since it uses less digits than its factorization.

1981390 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 198146.

The product of its (nonzero) digits is 1944, while the sum is 31.

The square root of 1981390 is about 1407.6185562858. The cubic root of 1981390 is about 125.6001010858.

The spelling of 1981390 in words is "one million, nine hundred eighty-one thousand, three hundred ninety".