15721121 has 8 divisors (see below), whose sum is σ = 17666880. Its totient is φ = 13880592.

The previous prime is 15721099. The next prime is 15721129. The reversal of 15721121 is 12112751.

It is a happy number.

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

It is not a de Polignac number, because 15721121 - 2¹⁴ = 15704737 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 15721093 and 15721102.

It is not an unprimeable number, because it can be changed into a prime (15721129) 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, 25991 + ... + 26588.

It is an arithmetic number, because the mean of its divisors is an integer number (2208360).

Almost surely, 2^15721121 is an apocalyptic number.

It is an amenable number.

15721121 is a deficient number, since it is larger than the sum of its proper divisors (1945759).

15721121 is a wasteful number, since it uses less digits than its factorization.

15721121 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 52615.

The product of its digits is 140, while the sum is 20.

The square root of 15721121 is about 3964.9868852242. The cubic root of 15721121 is about 250.5115976904.

Adding to 15721121 its reverse (12112751), we get a palindrome (27833872).

The spelling of 15721121 in words is "fifteen million, seven hundred twenty-one thousand, one hundred twenty-one".