15105721 has 2 divisors, whose sum is σ = 15105722. Its totient is φ = 15105720.

The previous prime is 15105709. The next prime is 15105743. The reversal of 15105721 is 12750151.

It is an a-pointer prime, because the next prime (15105743) can be obtained adding 15105721 to its sum of digits (22).

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 9517225 + 5588496 = 3085^2 + 2364^2 .

It is a cyclic number.

It is not a de Polignac number, because 15105721 - 2¹³ = 15097529 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 15105692 and 15105701.

It is not a weakly prime, because it can be changed into another prime (15105421) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 7552860 + 7552861.

It is an arithmetic number, because the mean of its divisors is an integer number (7552861).

Almost surely, 2^15105721 is an apocalyptic number.

It is an amenable number.

15105721 is a deficient number, since it is larger than the sum of its proper divisors (1).

15105721 is an equidigital number, since it uses as much as digits as its factorization.

15105721 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 350, while the sum is 22.

The square root of 15105721 is about 3886.6079040727. The cubic root of 15105721 is about 247.1992524232.

Adding to 15105721 its reverse (12750151), we get a palindrome (27855872).

The spelling of 15105721 in words is "fifteen million, one hundred five thousand, seven hundred twenty-one".