21364840 has 32 divisors (see below), whose sum is σ = 54938880. Its totient is φ = 7324992.

The previous prime is 21364817. The next prime is 21364841. The reversal of 21364840 is 4846312.

It is a Harshad number since it is a multiple of its sum of digits (28).

It is a junction number, because it is equal to n+sod(n) for n = 21364799 and 21364808.

It is not an unprimeable number, because it can be changed into a prime (21364841) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 37872 + ... + 38431.

It is an arithmetic number, because the mean of its divisors is an integer number (1716840).

Almost surely, 2^21364840 is an apocalyptic number.

21364840 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21364840 is an abundant number, since it is smaller than the sum of its proper divisors (33574040).

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

21364840 is a wasteful number, since it uses less digits than its factorization.

21364840 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 76321 (or 76317 counting only the distinct ones).

The product of its (nonzero) digits is 4608, while the sum is 28.

The square root of 21364840 is about 4622.2115918681. The cubic root of 21364840 is about 277.4809769715.

The spelling of 21364840 in words is "twenty-one million, three hundred sixty-four thousand, eight hundred forty".