16021656421 has 4 divisors (see below), whose sum is σ = 16035577344. Its totient is φ = 16007735500.

The previous prime is 16021656401. The next prime is 16021656433. The reversal of 16021656421 is 12465612061.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 12465612061 = 7 ⋅1780801723.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-16021656421 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (16021656401) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 6958735 + ... + 6961036.

It is an arithmetic number, because the mean of its divisors is an integer number (4008894336).

Almost surely, 2^16021656421 is an apocalyptic number.

It is an amenable number.

16021656421 is a deficient number, since it is larger than the sum of its proper divisors (13920923).

16021656421 is a wasteful number, since it uses less digits than its factorization.

16021656421 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 13920922.

The product of its (nonzero) digits is 17280, while the sum is 34.

The spelling of 16021656421 in words is "sixteen billion, twenty-one million, six hundred fifty-six thousand, four hundred twenty-one".