21389520 has 40 divisors (see below), whose sum is σ = 66308256. Its totient is φ = 5703808.

The previous prime is 21389509. The next prime is 21389521. The reversal of 21389520 is 2598312.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (40).

It is a Harshad number since it is a multiple of its sum of digits (30).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21389521) 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, 44322 + ... + 44801.

Almost surely, 2^21389520 is an apocalyptic number.

21389520 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21389520 is an abundant number, since it is smaller than the sum of its proper divisors (44918736).

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

21389520 is a wasteful number, since it uses less digits than its factorization.

21389520 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 89139 (or 89133 counting only the distinct ones).

The product of its (nonzero) digits is 4320, while the sum is 30.

The square root of 21389520 is about 4624.8805389977. The cubic root of 21389520 is about 277.5877816601.

The spelling of 21389520 in words is "twenty-one million, three hundred eighty-nine thousand, five hundred twenty".