15550021 has 2 divisors, whose sum is σ = 15550022. Its totient is φ = 15550020.

The previous prime is 15550009. The next prime is 15550039. The reversal of 15550021 is 12005551.

15550021 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 14364100 + 1185921 = 3790^2 + 1089^2 .

It is a cyclic number.

It is not a de Polignac number, because 15550021 - 2¹⁵ = 15517253 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (15550321) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 7775010 + 7775011.

It is an arithmetic number, because the mean of its divisors is an integer number (7775011).

Almost surely, 2^15550021 is an apocalyptic number.

It is an amenable number.

15550021 is a deficient number, since it is larger than the sum of its proper divisors (1).

15550021 is an equidigital number, since it uses as much as digits as its factorization.

15550021 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 250, while the sum is 19.

The square root of 15550021 is about 3943.3514933366. The cubic root of 15550021 is about 249.5994706476.

Adding to 15550021 its reverse (12005551), we get a palindrome (27555572).

It can be divided in two parts, 155 and 50021, that added together give a square (50176 = 224²).

The spelling of 15550021 in words is "fifteen million, five hundred fifty thousand, twenty-one".