15721642 has 4 divisors (see below), whose sum is σ = 23582466. Its totient is φ = 7860820.

The previous prime is 15721639. The next prime is 15721649. The reversal of 15721642 is 24612751.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 24612751 = 41 ⋅600311.

It can be written as a sum of positive squares in only one way, i.e., 15673681 + 47961 = 3959^2 + 219^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 15721642.

It is not an unprimeable number, because it can be changed into a prime (15721649) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 3930409 + ... + 3930412.

Almost surely, 2^15721642 is an apocalyptic number.

15721642 is a deficient number, since it is larger than the sum of its proper divisors (7860824).

15721642 is an equidigital number, since it uses as much as digits as its factorization.

15721642 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7860823.

The product of its digits is 3360, while the sum is 28.

The square root of 15721642 is about 3965.0525847711. The cubic root of 15721642 is about 250.5143649888.

The spelling of 15721642 in words is "fifteen million, seven hundred twenty-one thousand, six hundred forty-two".