21378634 has 16 divisors (see below), whose sum is σ = 32727240. Its totient is φ = 10471680.

The previous prime is 21378613. The next prime is 21378641. The reversal of 21378634 is 43687312.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 16769025 + 4609609 = 4095^2 + 2147^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 21378634.

It is an unprimeable number.

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 7 ways as a sum of consecutive naturals, for example, 26022 + ... + 26830.

Almost surely, 2^21378634 is an apocalyptic number.

21378634 is a deficient number, since it is larger than the sum of its proper divisors (11348606).

21378634 is a wasteful number, since it uses less digits than its factorization.

21378634 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1065.

The product of its digits is 24192, while the sum is 34.

The square root of 21378634 is about 4623.7034939537. The cubic root of 21378634 is about 277.5406817505.

The spelling of 21378634 in words is "twenty-one million, three hundred seventy-eight thousand, six hundred thirty-four".