1981390877 has 4 divisors (see below), whose sum is σ = 1983470940. Its totient is φ = 1979310816.

The previous prime is 1981390847. The next prime is 1981390883. The reversal of 1981390877 is 7780931891.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 7780931891 = 227 ⋅34277233.

It can be written as a sum of positive squares in 2 ways, for example, as 791071876 + 1190319001 = 28126^2 + 34501^2 .

It is a cyclic number.

It is not a de Polignac number, because 1981390877 - 2²⁸ = 1712955421 is a prime.

It is a super-3 number, since 3×1981390877³ (a number of 29 digits) contains 333 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 (1981390847) 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, 1038602 + ... + 1040507.

It is an arithmetic number, because the mean of its divisors is an integer number (495867735).

Almost surely, 2^1981390877 is an apocalyptic number.

It is an amenable number.

1981390877 is a deficient number, since it is larger than the sum of its proper divisors (2080063).

1981390877 is an equidigital number, since it uses as much as digits as its factorization.

1981390877 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2080062.

The product of its (nonzero) digits is 762048, while the sum is 53.

The square root of 1981390877 is about 44512.8169969055. The cubic root of 1981390877 is about 1256.0011961681.

The spelling of 1981390877 in words is "one billion, nine hundred eighty-one million, three hundred ninety thousand, eight hundred seventy-seven".