1391181721 has 8 divisors (see below), whose sum is σ = 1398336264. Its totient is φ = 1384037760.

The previous prime is 1391181719. The next prime is 1391181733. The reversal of 1391181721 is 1271811931.

It can be written as a sum of positive squares in 4 ways, for example, as 2576025 + 1388605696 = 1605^2 + 37264^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 1391181721 - 2¹ = 1391181719 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1391181521) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 435751 + ... + 438931.

It is an arithmetic number, because the mean of its divisors is an integer number (174792033).

Almost surely, 2^1391181721 is an apocalyptic number.

It is an amenable number.

1391181721 is a deficient number, since it is larger than the sum of its proper divisors (7154543).

1391181721 is a wasteful number, since it uses less digits than its factorization.

1391181721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5291.

The product of its digits is 3024, while the sum is 34.

The square root of 1391181721 is about 37298.5485106324. The cubic root of 1391181721 is about 1116.3352048763.

The spelling of 1391181721 in words is "one billion, three hundred ninety-one million, one hundred eighty-one thousand, seven hundred twenty-one".