16663621 has 8 divisors (see below), whose sum is σ = 19001304. Its totient is φ = 14476800.

The previous prime is 16663613. The next prime is 16663631. The reversal of 16663621 is 12636661.

16663621 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It can be written as a sum of positive squares in 4 ways, for example, as 1179396 + 15484225 = 1086^2 + 3935^2 .

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

It is not a de Polignac number, because 16663621 - 2³ = 16663613 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 (16663631) 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, 37480 + ... + 37921.

It is an arithmetic number, because the mean of its divisors is an integer number (2375163).

Almost surely, 2^16663621 is an apocalyptic number.

It is an amenable number.

16663621 is a deficient number, since it is larger than the sum of its proper divisors (2337683).

16663621 is a wasteful number, since it uses less digits than its factorization.

16663621 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 75431.

The product of its digits is 7776, while the sum is 31.

The square root of 16663621 is about 4082.1098711328. The cubic root of 16663621 is about 255.4209170293.

The spelling of 16663621 in words is "sixteen million, six hundred sixty-three thousand, six hundred twenty-one".