21643455 has 16 divisors (see below), whose sum is σ = 34938720. Its totient is φ = 11441024.

The previous prime is 21643429. The next prime is 21643507. The reversal of 21643455 is 55434612.

It is not a de Polignac number, because 21643455 - 2¹⁴ = 21627071 is a prime.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 191479 + ... + 191591.

It is an arithmetic number, because the mean of its divisors is an integer number (2183670).

Almost surely, 2^21643455 is an apocalyptic number.

21643455 is a deficient number, since it is larger than the sum of its proper divisors (13295265).

21643455 is an frugal number, since it uses more digits than its factorization.

21643455 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 347 (or 121 counting only the distinct ones).

The product of its digits is 14400, while the sum is 30.

The square root of 21643455 is about 4652.2526801540. The cubic root of 21643455 is about 278.6819643993.

Multiplying 21643455 by its product of digits (14400), we get a cube (311665752000 = 6780³).

The spelling of 21643455 in words is "twenty-one million, six hundred forty-three thousand, four hundred fifty-five".