189777981 has 4 divisors (see below), whose sum is σ = 253037312. Its totient is φ = 126518652.

The previous prime is 189777977. The next prime is 189778003.

189777981 is nontrivially palindromic in base 10.

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 not a de Polignac number, because 189777981 - 2² = 189777977 is a prime.

It is a super-2 number, since 2×189777981² = 72031364144872722, which contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (189777901) 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, 31629661 + ... + 31629666.

It is an arithmetic number, because the mean of its divisors is an integer number (63259328).

Almost surely, 2^189777981 is an apocalyptic number.

It is an amenable number.

189777981 is a deficient number, since it is larger than the sum of its proper divisors (63259331).

189777981 is an equidigital number, since it uses as much as digits as its factorization.

189777981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 63259330.

The product of its digits is 1778112, while the sum is 57.

The square root of 189777981 is about 13775.9929224720. The cubic root of 189777981 is about 574.6656970425.

The spelling of 189777981 in words is "one hundred eighty-nine million, seven hundred seventy-seven thousand, nine hundred eighty-one".