21361387 has 4 divisors (see below), whose sum is σ = 22050496. Its totient is φ = 20672280.

The previous prime is 21361303. The next prime is 21361391. The reversal of 21361387 is 78316312.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21361387 - 2⁷ = 21361259 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (31), and also a Moran number because the ratio is a prime number: 689077 = 21361387 / (2 + 1 + 3 + 6 + 1 + 3 + 8 + 7).

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21361397) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 344508 + ... + 344569.

It is an arithmetic number, because the mean of its divisors is an integer number (5512624).

Almost surely, 2^21361387 is an apocalyptic number.

21361387 is a deficient number, since it is larger than the sum of its proper divisors (689109).

21361387 is an equidigital number, since it uses as much as digits as its factorization.

21361387 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 689108.

The product of its digits is 6048, while the sum is 31.

The square root of 21361387 is about 4621.8380542810. The cubic root of 21361387 is about 277.4660272779.

Adding to 21361387 its reverse (78316312), we get a palindrome (99677699).

The spelling of 21361387 in words is "twenty-one million, three hundred sixty-one thousand, three hundred eighty-seven".