16721531425 has 6 divisors (see below), whose sum is σ = 20734698998. Its totient is φ = 13377225120.

The previous prime is 16721531413. The next prime is 16721531443. The reversal of 16721531425 is 52413512761.

It can be written as a sum of positive squares in 3 ways, for example, as 244985104 + 16476546321 = 15652^2 + 128361^2 .

It is not a de Polignac number, because 16721531425 - 2²⁵ = 16687976993 is a prime.

It is a super-2 number, since 2×16721531425² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 334430604 + ... + 334430653.

Almost surely, 2^16721531425 is an apocalyptic number.

It is an amenable number.

16721531425 is a deficient number, since it is larger than the sum of its proper divisors (4013167573).

16721531425 is an equidigital number, since it uses as much as digits as its factorization.

16721531425 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 668861267 (or 668861262 counting only the distinct ones).

The product of its digits is 50400, while the sum is 37.

The spelling of 16721531425 in words is "sixteen billion, seven hundred twenty-one million, five hundred thirty-one thousand, four hundred twenty-five".