16721531345 has 4 divisors (see below), whose sum is σ = 20065837620. Its totient is φ = 13377225072.

The previous prime is 16721531293. The next prime is 16721531413. The reversal of 16721531345 is 54313512761.

It is a happy number.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 2591929921 + 14129601424 = 50911^2 + 118868^2 .

It is a cyclic number.

It is not a de Polignac number, because 16721531345 - 2⁸ = 16721531089 is a prime.

It is a super-2 number, since 2×16721531345² (a number of 21 digits) contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 16721531299 and 16721531308.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1672153130 + ... + 1672153139.

It is an arithmetic number, because the mean of its divisors is an integer number (5016459405).

Almost surely, 2^16721531345 is an apocalyptic number.

It is an amenable number.

16721531345 is a deficient number, since it is larger than the sum of its proper divisors (3344306275).

16721531345 is an equidigital number, since it uses as much as digits as its factorization.

16721531345 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3344306274.

The product of its digits is 75600, while the sum is 38.

The spelling of 16721531345 in words is "sixteen billion, seven hundred twenty-one million, five hundred thirty-one thousand, three hundred forty-five".