21017408 has 14 divisors (see below), whose sum is σ = 41706546. Its totient is φ = 10508672.

The previous prime is 21017407. The next prime is 21017419. The reversal of 21017408 is 80471012.

It can be written as a sum of positive squares in only one way, i.e., 16386304 + 4631104 = 4048^2 + 2152^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21017407) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 164135 + ... + 164262.

It is an arithmetic number, because the mean of its divisors is an integer number (2979039).

Almost surely, 2^21017408 is an apocalyptic number.

It is an amenable number.

21017408 is a deficient number, since it is larger than the sum of its proper divisors (20689138).

21017408 is an equidigital number, since it uses as much as digits as its factorization.

21017408 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 328409 (or 328399 counting only the distinct ones).

The product of its (nonzero) digits is 448, while the sum is 23.

The square root of 21017408 is about 4584.4746700140. The cubic root of 21017408 is about 275.9686304752.

The spelling of 21017408 in words is "twenty-one million, seventeen thousand, four hundred eight".