1731720421 has 4 divisors (see below), whose sum is σ = 1747904832. Its totient is φ = 1715536012.

The previous prime is 1731720373. The next prime is 1731720427. The reversal of 1731720421 is 1240271371.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 1240271371 = 67 ⋅18511513.

It is a cyclic number.

It is not a de Polignac number, because 1731720421 - 2⁷ = 1731720293 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 1731720421.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1731720427) 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, 8092045 + ... + 8092258.

It is an arithmetic number, because the mean of its divisors is an integer number (436976208).

Almost surely, 2^1731720421 is an apocalyptic number.

It is an amenable number.

1731720421 is a deficient number, since it is larger than the sum of its proper divisors (16184411).

1731720421 is a wasteful number, since it uses less digits than its factorization.

1731720421 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 16184410.

The product of its (nonzero) digits is 2352, while the sum is 28.

The square root of 1731720421 is about 41613.9450304823. The cubic root of 1731720421 is about 1200.8605912362.

Adding to 1731720421 its reverse (1240271371), we get a palindrome (2971991792).

The spelling of 1731720421 in words is "one billion, seven hundred thirty-one million, seven hundred twenty thousand, four hundred twenty-one".