21378655 has 16 divisors (see below), whose sum is σ = 27112320. Its totient is φ = 16156672.

The previous prime is 21378653. The next prime is 21378659. The reversal of 21378655 is 55687312.

It is a cyclic number.

It is not a de Polignac number, because 21378655 - 2¹ = 21378653 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21378653) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 5247 + ... + 8383.

It is an arithmetic number, because the mean of its divisors is an integer number (1694520).

Almost surely, 2^21378655 is an apocalyptic number.

21378655 is a deficient number, since it is larger than the sum of its proper divisors (5733665).

21378655 is a wasteful number, since it uses less digits than its factorization.

21378655 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3218.

The product of its digits is 50400, while the sum is 37.

The square root of 21378655 is about 4623.7057648600. The cubic root of 21378655 is about 277.5407726255.

The spelling of 21378655 in words is "twenty-one million, three hundred seventy-eight thousand, six hundred fifty-five".