15717421 has 4 divisors (see below), whose sum is σ = 15726492. Its totient is φ = 15708352.

The previous prime is 15717419. The next prime is 15717431. The reversal of 15717421 is 12471751.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in 2 ways, for example, as 6687396 + 9030025 = 2586^2 + 3005^2 .

It is a cyclic number.

It is not a de Polignac number, because 15717421 - 2¹ = 15717419 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 15717421.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (15717431) 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, 1036 + ... + 5701.

It is an arithmetic number, because the mean of its divisors is an integer number (3931623).

Almost surely, 2^15717421 is an apocalyptic number.

It is an amenable number.

15717421 is a deficient number, since it is larger than the sum of its proper divisors (9071).

15717421 is an equidigital number, since it uses as much as digits as its factorization.

15717421 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9070.

The product of its digits is 1960, while the sum is 28.

The square root of 15717421 is about 3964.5202736271. The cubic root of 15717421 is about 250.4919433321.

It can be divided in two parts, 157 and 17421, that added together give a triangular number (17578 = T₁₈₇).

The spelling of 15717421 in words is "fifteen million, seven hundred seventeen thousand, four hundred twenty-one".