21020408 has 16 divisors (see below), whose sum is σ = 39676560. Its totient is φ = 10440000.

The previous prime is 21020407. The next prime is 21020411. The reversal of 21020408 is 80402012.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21020407) 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 3 ways as a sum of consecutive naturals, for example, 7493 + ... + 9908.

It is an arithmetic number, because the mean of its divisors is an integer number (2479785).

Almost surely, 2^21020408 is an apocalyptic number.

It is an amenable number.

21020408 is a deficient number, since it is larger than the sum of its proper divisors (18656152).

21020408 is a wasteful number, since it uses less digits than its factorization.

21020408 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 17558 (or 17554 counting only the distinct ones).

The product of its (nonzero) digits is 128, while the sum is 17.

The square root of 21020408 is about 4584.8018495896. The cubic root of 21020408 is about 275.9817603293.

The spelling of 21020408 in words is "twenty-one million, twenty thousand, four hundred eight".