1491892781 has 4 divisors (see below), whose sum is σ = 1492264572. Its totient is φ = 1491520992.

The previous prime is 1491892777. The next prime is 1491892793. The reversal of 1491892781 is 1872981941.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 1872981941 = 15139 ⋅123719.

It can be written as a sum of positive squares in 2 ways, for example, as 1140142756 + 351750025 = 33766^2 + 18755^2 .

It is a cyclic number.

It is not a de Polignac number, because 1491892781 - 2² = 1491892777 is a prime.

It is a super-2 number, since 2×1491892781² = 4451488139999827922, which contains 22 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 (1491892741) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 179810 + ... + 187923.

It is an arithmetic number, because the mean of its divisors is an integer number (373066143).

Almost surely, 2^1491892781 is an apocalyptic number.

It is an amenable number.

1491892781 is a deficient number, since it is larger than the sum of its proper divisors (371791).

1491892781 is an equidigital number, since it uses as much as digits as its factorization.

1491892781 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 371790.

The product of its digits is 290304, while the sum is 50.

The square root of 1491892781 is about 38625.0279093750. The cubic root of 1491892781 is about 1142.6481938559.

The spelling of 1491892781 in words is "one billion, four hundred ninety-one million, eight hundred ninety-two thousand, seven hundred eighty-one".