21003388 has 12 divisors (see below), whose sum is σ = 42006832. Its totient is φ = 9001440.

The previous prime is 21003373. The next prime is 21003397. The reversal of 21003388 is 88330012.

21003388 is an admirable number.

It is a super-2 number, since 2×21003388² = 882284614957088, which contains 22 as substring.

It is a hoax number, since the sum of its digits (25) coincides with the sum of the digits of its distinct prime factors.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 375033 + ... + 375088.

Almost surely, 2^21003388 is an apocalyptic number.

21003388 is a gapful number since it is divisible by the number (28) formed by its first and last digit.

It is an amenable number.

21003388 is a primitive abundant number, since it is smaller than the sum of its proper divisors, none of which is abundant.

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21003388 is a wasteful number, since it uses less digits than its factorization.

21003388 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 750132 (or 750130 counting only the distinct ones).

The product of its (nonzero) digits is 1152, while the sum is 25.

The square root of 21003388 is about 4582.9453411534. The cubic root of 21003388 is about 275.9072537214.

The spelling of 21003388 in words is "twenty-one million, three thousand, three hundred eighty-eight".