21472821 has 12 divisors (see below), whose sum is σ = 31056480. Its totient is φ = 14296680.

The previous prime is 21472817. The next prime is 21472849. The reversal of 21472821 is 12827412.

It is not a de Polignac number, because 21472821 - 2² = 21472817 is a prime.

It is a super-2 number, since 2×21472821² = 922164083396082, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21472021) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 12810 + ... + 14388.

It is an arithmetic number, because the mean of its divisors is an integer number (2588040).

Almost surely, 2^21472821 is an apocalyptic number.

It is an amenable number.

21472821 is a deficient number, since it is larger than the sum of its proper divisors (9583659).

21472821 is a wasteful number, since it uses less digits than its factorization.

21472821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3096 (or 3093 counting only the distinct ones).

The product of its digits is 1792, while the sum is 27.

The square root of 21472821 is about 4633.8775339881. The cubic root of 21472821 is about 277.9476679784.

The spelling of 21472821 in words is "twenty-one million, four hundred seventy-two thousand, eight hundred twenty-one".