15720409 has 2 divisors, whose sum is σ = 15720410. Its totient is φ = 15720408.

The previous prime is 15720389. The next prime is 15720421. The reversal of 15720409 is 90402751.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 15681600 + 38809 = 3960^2 + 197^2 .

It is an emirp because it is prime and its reverse (90402751) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 15720409 - 2⁵ = 15720377 is a prime.

It is not a weakly prime, because it can be changed into another prime (15720469) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 7860204 + 7860205.

It is an arithmetic number, because the mean of its divisors is an integer number (7860205).

Almost surely, 2^15720409 is an apocalyptic number.

It is an amenable number.

15720409 is a deficient number, since it is larger than the sum of its proper divisors (1).

15720409 is an equidigital number, since it uses as much as digits as its factorization.

15720409 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 2520, while the sum is 28.

The square root of 15720409 is about 3964.8970982864. The cubic root of 15720409 is about 250.5078157941.

It can be divided in two parts, 15720 and 409, that added together give a square (16129 = 127²).

The spelling of 15720409 in words is "fifteen million, seven hundred twenty thousand, four hundred nine".