1720138391 has 8 divisors (see below), whose sum is σ = 1728324864. Its totient is φ = 1711963000.

The previous prime is 1720138379. The next prime is 1720138411. The reversal of 1720138391 is 1938310271.

It is a happy number.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1720138391 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1720138361) 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 7 ways as a sum of consecutive naturals, for example, 567506 + ... + 570528.

It is an arithmetic number, because the mean of its divisors is an integer number (216040608).

Almost surely, 2^1720138391 is an apocalyptic number.

1720138391 is a deficient number, since it is larger than the sum of its proper divisors (8186473).

1720138391 is a wasteful number, since it uses less digits than its factorization.

1720138391 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5541.

The product of its (nonzero) digits is 9072, while the sum is 35.

The square root of 1720138391 is about 41474.5511247560. The cubic root of 1720138391 is about 1198.1774163273.

The spelling of 1720138391 in words is "one billion, seven hundred twenty million, one hundred thirty-eight thousand, three hundred ninety-one".