1977816121 has 4 divisors (see below), whose sum is σ = 1980638244. Its totient is φ = 1974994000.

The previous prime is 1977816109. The next prime is 1977816131. The reversal of 1977816121 is 1216187791.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 1758628096 + 219188025 = 41936^2 + 14805^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1977816121 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1977816131) 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, 1410010 + ... + 1411411.

It is an arithmetic number, because the mean of its divisors is an integer number (495159561).

Almost surely, 2^1977816121 is an apocalyptic number.

It is an amenable number.

1977816121 is a deficient number, since it is larger than the sum of its proper divisors (2822123).

1977816121 is an equidigital number, since it uses as much as digits as its factorization.

1977816121 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2822122.

The product of its digits is 42336, while the sum is 43.

The square root of 1977816121 is about 44472.6446369001. The cubic root of 1977816121 is about 1255.2453970060.

The spelling of 1977816121 in words is "one billion, nine hundred seventy-seven million, eight hundred sixteen thousand, one hundred twenty-one".