16720515421 has 2 divisors, whose sum is σ = 16720515422. Its totient is φ = 16720515420.

The previous prime is 16720515391. The next prime is 16720515433. The reversal of 16720515421 is 12451502761.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 10319715396 + 6400800025 = 101586^2 + 80005^2 .

It is a cyclic number.

It is not a de Polignac number, because 16720515421 - 2⁵ = 16720515389 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (16720515521) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 8360257710 + 8360257711.

It is an arithmetic number, because the mean of its divisors is an integer number (8360257711).

Almost surely, 2^16720515421 is an apocalyptic number.

It is an amenable number.

16720515421 is a deficient number, since it is larger than the sum of its proper divisors (1).

16720515421 is an equidigital number, since it uses as much as digits as its factorization.

16720515421 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 16800, while the sum is 34.

The spelling of 16720515421 in words is "sixteen billion, seven hundred twenty million, five hundred fifteen thousand, four hundred twenty-one".