16221428 has 6 divisors (see below), whose sum is σ = 28387506. Its totient is φ = 8110712.

The previous prime is 16221391. The next prime is 16221431. The reversal of 16221428 is 82412261.

It is a happy number.

It can be written as a sum of positive squares in only one way, i.e., 16176484 + 44944 = 4022^2 + 212^2 .

It is a junction number, because it is equal to n+sod(n) for n = 16221397 and 16221406.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2027675 + ... + 2027682.

It is an arithmetic number, because the mean of its divisors is an integer number (4731251).

Almost surely, 2^16221428 is an apocalyptic number.

It is an amenable number.

16221428 is a deficient number, since it is larger than the sum of its proper divisors (12166078).

16221428 is a wasteful number, since it uses less digits than its factorization.

16221428 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4055361 (or 4055359 counting only the distinct ones).

The product of its digits is 1536, while the sum is 26.

The square root of 16221428 is about 4027.5833945432. The cubic root of 16221428 is about 253.1413126306.

Adding to 16221428 its reverse (82412261), we get a palindrome (98633689).

The spelling of 16221428 in words is "sixteen million, two hundred twenty-one thousand, four hundred twenty-eight".