21387420 has 36 divisors (see below), whose sum is σ = 64875720. Its totient is φ = 5703264.

The previous prime is 21387419. The next prime is 21387437. The reversal of 21387420 is 2478312.

It is a tau number, because it is divible by the number of its divisors (36).

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 59230 + ... + 59589.

Almost surely, 2^21387420 is an apocalyptic number.

21387420 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21387420 is an abundant number, since it is smaller than the sum of its proper divisors (43488300).

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

21387420 is a wasteful number, since it uses less digits than its factorization.

21387420 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 118834 (or 118829 counting only the distinct ones).

The product of its (nonzero) digits is 2688, while the sum is 27.

The square root of 21387420 is about 4624.6535005339. The cubic root of 21387420 is about 277.5786969398.

The spelling of 21387420 in words is "twenty-one million, three hundred eighty-seven thousand, four hundred twenty".