1721040021 has 16 divisors (see below), whose sum is σ = 2660545920. Its totient is φ = 1097474400.

The previous prime is 1721040019. The next prime is 1721040029. The reversal of 1721040021 is 1200401271.

It is not a de Polignac number, because 1721040021 - 2¹ = 1721040019 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 1721039976 and 1721040003.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1721040029) 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 15 ways as a sum of consecutive naturals, for example, 1385080 + ... + 1386321.

It is an arithmetic number, because the mean of its divisors is an integer number (166284120).

Almost surely, 2^1721040021 is an apocalyptic number.

It is an amenable number.

1721040021 is a deficient number, since it is larger than the sum of its proper divisors (939505899).

1721040021 is a wasteful number, since it uses less digits than its factorization.

1721040021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2771433 (or 2771427 counting only the distinct ones).

The product of its (nonzero) digits is 112, while the sum is 18.

The square root of 1721040021 is about 41485.4193783792. The cubic root of 1721040021 is about 1198.3867258440.

Adding to 1721040021 its reverse (1200401271), we get a palindrome (2921441292).

The spelling of 1721040021 in words is "one billion, seven hundred twenty-one million, forty thousand, twenty-one".