16721421 has 8 divisors (see below), whose sum is σ = 23606784. Its totient is φ = 10491840.

The previous prime is 16721417. The next prime is 16721443. The reversal of 16721421 is 12412761.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 16721421 - 2² = 16721417 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 16721391 and 16721400.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (16721461) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 163885 + ... + 163986.

It is an arithmetic number, because the mean of its divisors is an integer number (2950848).

Almost surely, 2^16721421 is an apocalyptic number.

It is an amenable number.

16721421 is a deficient number, since it is larger than the sum of its proper divisors (6885363).

16721421 is a wasteful number, since it uses less digits than its factorization.

16721421 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 327891.

The product of its digits is 672, while the sum is 24.

The square root of 16721421 is about 4089.1834148152. The cubic root of 16721421 is about 255.7158967798.

The spelling of 16721421 in words is "sixteen million, seven hundred twenty-one thousand, four hundred twenty-one".