16721621 has 16 divisors (see below), whose sum is σ = 20066304. Its totient is φ = 13623984.

The previous prime is 16721611. The next prime is 16721629. The reversal of 16721621 is 12612761.

It is a cyclic number.

It is not a de Polignac number, because 16721621 - 2¹⁰ = 16720597 is a prime.

It is a super-2 number, since 2×16721621² = 559225217735282, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (16721629) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 45380 + ... + 45746.

It is an arithmetic number, because the mean of its divisors is an integer number (1254144).

Almost surely, 2^16721621 is an apocalyptic number.

It is an amenable number.

16721621 is a deficient number, since it is larger than the sum of its proper divisors (3344683).

16721621 is a wasteful number, since it uses less digits than its factorization.

16721621 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 680.

The product of its digits is 1008, while the sum is 26.

The square root of 16721621 is about 4089.2078695024. The cubic root of 16721621 is about 255.7169162900.

The spelling of 16721621 in words is "sixteen million, seven hundred twenty-one thousand, six hundred twenty-one".