1618781491 has 4 divisors (see below), whose sum is σ = 1649324592. Its totient is φ = 1588238392.

The previous prime is 1618781477. The next prime is 1618781503. The reversal of 1618781491 is 1941878161.

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

It is a cyclic number.

It is not a de Polignac number, because 1618781491 - 2¹¹ = 1618779443 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1618781401) 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, 15271471 + ... + 15271576.

It is an arithmetic number, because the mean of its divisors is an integer number (412331148).

Almost surely, 2^1618781491 is an apocalyptic number.

1618781491 is a deficient number, since it is larger than the sum of its proper divisors (30543101).

1618781491 is an equidigital number, since it uses as much as digits as its factorization.

1618781491 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 30543100.

The product of its digits is 96768, while the sum is 46.

The square root of 1618781491 is about 40234.0836977804. The cubic root of 1618781491 is about 1174.1657554387.

The spelling of 1618781491 in words is "one billion, six hundred eighteen million, seven hundred eighty-one thousand, four hundred ninety-one".