1618978981 has 2 divisors, whose sum is σ = 1618978982. Its totient is φ = 1618978980.

The previous prime is 1618978973. The next prime is 1618978987. The reversal of 1618978981 is 1898798161.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1584756481 + 34222500 = 39809^2 + 5850^2 .

It is a cyclic number.

It is not a de Polignac number, because 1618978981 - 2³ = 1618978973 is a prime.

It is a super-2 number, since 2×1618978981² = 5242185881839596722, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1618978987) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 809489490 + 809489491.

It is an arithmetic number, because the mean of its divisors is an integer number (809489491).

Almost surely, 2^1618978981 is an apocalyptic number.

It is an amenable number.

1618978981 is a deficient number, since it is larger than the sum of its proper divisors (1).

1618978981 is an equidigital number, since it uses as much as digits as its factorization.

1618978981 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1741824, while the sum is 58.

The square root of 1618978981 is about 40236.5378853599. The cubic root of 1618978981 is about 1174.2135025800.

The spelling of 1618978981 in words is "one billion, six hundred eighteen million, nine hundred seventy-eight thousand, nine hundred eighty-one".