15221421 has 6 divisors (see below), whose sum is σ = 21986510. Its totient is φ = 10147608.

The previous prime is 15221417. The next prime is 15221431. The reversal of 15221421 is 12412251.

15221421 is a `hidden beast` number, since 1 + 522 + 142 + 1 = 666.

It can be written as a sum of positive squares in only one way, i.e., 14356521 + 864900 = 3789^2 + 930^2 .

It is not a de Polignac number, because 15221421 - 2² = 15221417 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 15221394 and 15221403.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (15221411) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 845626 + ... + 845643.

Almost surely, 2^15221421 is an apocalyptic number.

It is an amenable number.

15221421 is a deficient number, since it is larger than the sum of its proper divisors (6765089).

15221421 is a wasteful number, since it uses less digits than its factorization.

15221421 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1691275 (or 1691272 counting only the distinct ones).

The product of its digits is 160, while the sum is 18.

The square root of 15221421 is about 3901.4639560042. The cubic root of 15221421 is about 247.8287764090.

Subtracting from 15221421 its sum of digits (18), we obtain a triangular number (15221403 = T₅₅₁₇).

Adding to 15221421 its reverse (12412251), we get a palindrome (27633672).

The spelling of 15221421 in words is "fifteen million, two hundred twenty-one thousand, four hundred twenty-one".