15665421 has 8 divisors (see below), whose sum is σ = 20920960. Its totient is φ = 10426752.

The previous prime is 15665417. The next prime is 15665437. The reversal of 15665421 is 12456651.

15665421 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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

It is not a de Polignac number, because 15665421 - 2² = 15665417 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 (15665401) 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, 1861 + ... + 5898.

It is an arithmetic number, because the mean of its divisors is an integer number (2615120).

Almost surely, 2^15665421 is an apocalyptic number.

It is an amenable number.

15665421 is a deficient number, since it is larger than the sum of its proper divisors (5255539).

15665421 is an equidigital number, since it uses as much as digits as its factorization.

15665421 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8435.

The product of its digits is 7200, while the sum is 30.

The square root of 15665421 is about 3957.9566697982. The cubic root of 15665421 is about 250.2153930367.

The spelling of 15665421 in words is "fifteen million, six hundred sixty-five thousand, four hundred twenty-one".