21378567 has 16 divisors (see below), whose sum is σ = 32647680. Its totient is φ = 12189792.

The previous prime is 21378547. The next prime is 21378587. The reversal of 21378567 is 76587312.

It is an interprime number because it is at equal distance from previous prime (21378547) and next prime (21378587).

It is not a de Polignac number, because 21378567 - 2¹¹ = 21376519 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21378527) 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 15 ways as a sum of consecutive naturals, for example, 12934 + ... + 14492.

It is an arithmetic number, because the mean of its divisors is an integer number (2040480).

Almost surely, 2^21378567 is an apocalyptic number.

21378567 is a deficient number, since it is larger than the sum of its proper divisors (11269113).

21378567 is a wasteful number, since it uses less digits than its factorization.

21378567 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2222.

The product of its digits is 70560, while the sum is 39.

The square root of 21378567 is about 4623.6962486738. The cubic root of 21378567 is about 277.5403918154.

It can be divided in two parts, 21378 and 567, that added together give a triangular number (21945 = T₂₀₉).

The spelling of 21378567 in words is "twenty-one million, three hundred seventy-eight thousand, five hundred sixty-seven".