15642221 has 12 divisors (see below), whose sum is σ = 18449532. Its totient is φ = 13220928.

The previous prime is 15642217. The next prime is 15642247. The reversal of 15642221 is 12224651.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 8934121 + 6708100 = 2989^2 + 2590^2 .

It is not a de Polignac number, because 15642221 - 2² = 15642217 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (15642271) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 1391 + ... + 5763.

It is an arithmetic number, because the mean of its divisors is an integer number (1537461).

Almost surely, 2^15642221 is an apocalyptic number.

It is an amenable number.

15642221 is a deficient number, since it is larger than the sum of its proper divisors (2807311).

15642221 is an equidigital number, since it uses as much as digits as its factorization.

15642221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4460 (or 4453 counting only the distinct ones).

The product of its digits is 960, while the sum is 23.

The square root of 15642221 is about 3955.0247786834. The cubic root of 15642221 is about 250.0918116117.

Adding to 15642221 its reverse (12224651), we get a palindrome (27866872).

The spelling of 15642221 in words is "fifteen million, six hundred forty-two thousand, two hundred twenty-one".