16521221042 has 4 divisors (see below), whose sum is σ = 24781831566. Its totient is φ = 8260610520.

The previous prime is 16521221009. The next prime is 16521221077. The reversal of 16521221042 is 24012212561.

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

It can be written as a sum of positive squares in only one way, i.e., 13507320841 + 3013900201 = 116221^2 + 54899^2 .

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 4130305259 + ... + 4130305262.

Almost surely, 2^16521221042 is an apocalyptic number.

16521221042 is a deficient number, since it is larger than the sum of its proper divisors (8260610524).

16521221042 is an equidigital number, since it uses as much as digits as its factorization.

16521221042 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8260610523.

The product of its (nonzero) digits is 1920, while the sum is 26.

The spelling of 16521221042 in words is "sixteen billion, five hundred twenty-one million, two hundred twenty-one thousand, forty-two".