21447428 has 24 divisors (see below), whose sum is σ = 40477920. Its totient is φ = 9910080.

The previous prime is 21447427. The next prime is 21447509. The reversal of 21447428 is 82474412.

It is a junction number, because it is equal to n+sod(n) for n = 21447394 and 21447403.

It is not an unprimeable number, because it can be changed into a prime (21447427) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 326 + ... + 6557.

It is an arithmetic number, because the mean of its divisors is an integer number (1686580).

Almost surely, 2^21447428 is an apocalyptic number.

It is an amenable number.

21447428 is a deficient number, since it is larger than the sum of its proper divisors (19030492).

21447428 is a wasteful number, since it uses less digits than its factorization.

21447428 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6947 (or 6945 counting only the distinct ones).

The product of its digits is 14336, while the sum is 32.

The square root of 21447428 is about 4631.1367934882. The cubic root of 21447428 is about 277.8380610616.

The spelling of 21447428 in words is "twenty-one million, four hundred forty-seven thousand, four hundred twenty-eight".