1720831621 has 2 divisors, whose sum is σ = 1720831622. Its totient is φ = 1720831620.

The previous prime is 1720831603. The next prime is 1720831657. The reversal of 1720831621 is 1261380271.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1665864225 + 54967396 = 40815^2 + 7414^2 .

It is an emirp because it is prime and its reverse (1261380271) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 1720831621 - 2²¹ = 1718734469 is a prime.

It is a super-2 number, since 2×1720831621² = 5922522935666975282, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1720831601) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 860415810 + 860415811.

It is an arithmetic number, because the mean of its divisors is an integer number (860415811).

Almost surely, 2^1720831621 is an apocalyptic number.

It is an amenable number.

1720831621 is a deficient number, since it is larger than the sum of its proper divisors (1).

1720831621 is an equidigital number, since it uses as much as digits as its factorization.

1720831621 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 4032, while the sum is 31.

The square root of 1720831621 is about 41482.9075764947. The cubic root of 1720831621 is about 1198.3383531795.

The spelling of 1720831621 in words is "one billion, seven hundred twenty million, eight hundred thirty-one thousand, six hundred twenty-one".