189399981 has 4 divisors (see below), whose sum is σ = 252533312. Its totient is φ = 126266652.

The previous prime is 189399979. The next prime is 189399983. The reversal of 189399981 is 189993981.

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 (189399979) and next prime (189399983).

It is not a de Polignac number, because 189399981 - 2¹ = 189399979 is a prime.

It is a super-2 number, since 2×189399981² = 71744705605600722, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (189399983) 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, 31566661 + ... + 31566666.

It is an arithmetic number, because the mean of its divisors is an integer number (63133328).

Almost surely, 2^189399981 is an apocalyptic number.

It is an amenable number.

189399981 is a deficient number, since it is larger than the sum of its proper divisors (63133331).

189399981 is an equidigital number, since it uses as much as digits as its factorization.

189399981 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 63133330.

The product of its digits is 1259712, while the sum is 57.

The square root of 189399981 is about 13762.2665647778. The cubic root of 189399981 is about 574.2839035133.

It can be divided in two parts, 18939 and 9981, that added together give a triangular number (28920 = T₂₄₀).

The spelling of 189399981 in words is "one hundred eighty-nine million, three hundred ninety-nine thousand, nine hundred eighty-one".