21366387 has 24 divisors (see below), whose sum is σ = 35449440. Its totient is φ = 12147840.

The previous prime is 21366377. The next prime is 21366391. The reversal of 21366387 is 78366312.

It is a happy number.

21366387 is a `hidden beast` number, since 2 + 13 + 6 + 638 + 7 = 666.

It is not a de Polignac number, because 21366387 - 2⁷ = 21366259 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21366377) by changing a digit.

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 23 ways as a sum of consecutive naturals, for example, 13687 + ... + 15167.

It is an arithmetic number, because the mean of its divisors is an integer number (1477060).

Almost surely, 2^21366387 is an apocalyptic number.

21366387 is a deficient number, since it is larger than the sum of its proper divisors (14083053).

21366387 is a wasteful number, since it uses less digits than its factorization.

21366387 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1723 (or 1720 counting only the distinct ones).

The product of its digits is 36288, while the sum is 36.

The square root of 21366387 is about 4622.3789329738. The cubic root of 21366387 is about 277.4876741543.

The spelling of 21366387 in words is "twenty-one million, three hundred sixty-six thousand, three hundred eighty-seven".