21378369 has 4 divisors (see below), whose sum is σ = 28504496. Its totient is φ = 14252244.

The previous prime is 21378361. The next prime is 21378389. The reversal of 21378369 is 96387312.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 21378369 - 2³ = 21378361 is a prime.

It is a super-2 number, since 2×21378369² = 914069322200322, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21378361) 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, 3563059 + ... + 3563064.

It is an arithmetic number, because the mean of its divisors is an integer number (7126124).

Almost surely, 2^21378369 is an apocalyptic number.

It is an amenable number.

21378369 is a deficient number, since it is larger than the sum of its proper divisors (7126127).

21378369 is an equidigital number, since it uses as much as digits as its factorization.

21378369 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7126126.

The product of its digits is 54432, while the sum is 39.

The square root of 21378369 is about 4623.6748371831. The cubic root of 21378369 is about 277.5395349889.

The spelling of 21378369 in words is "twenty-one million, three hundred seventy-eight thousand, three hundred sixty-nine".