21168428 has 6 divisors (see below), whose sum is σ = 37044756. Its totient is φ = 10584212.

The previous prime is 21168409. The next prime is 21168439. The reversal of 21168428 is 82486112.

It is a happy number.

It is a junction number, because it is equal to n+sod(n) for n = 21168394 and 21168403.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2646050 + ... + 2646057.

It is an arithmetic number, because the mean of its divisors is an integer number (6174126).

Almost surely, 2^21168428 is an apocalyptic number.

It is an amenable number.

21168428 is a deficient number, since it is larger than the sum of its proper divisors (15876328).

21168428 is a wasteful number, since it uses less digits than its factorization.

21168428 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5292111 (or 5292109 counting only the distinct ones).

The product of its digits is 6144, while the sum is 32.

The square root of 21168428 is about 4600.9159957556. The cubic root of 21168428 is about 276.6280418975.

The spelling of 21168428 in words is "twenty-one million, one hundred sixty-eight thousand, four hundred twenty-eight".