21554643 has 32 divisors (see below), whose sum is σ = 32659200. Its totient is φ = 12531200.

The previous prime is 21554639. The next prime is 21554651. The reversal of 21554643 is 34645512.

It is not a de Polignac number, because 21554643 - 2² = 21554639 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21554643.

It is not an unprimeable number, because it can be changed into a prime (21554633) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 120328 + ... + 120506.

It is an arithmetic number, because the mean of its divisors is an integer number (1020600).

Almost surely, 2^21554643 is an apocalyptic number.

21554643 is a deficient number, since it is larger than the sum of its proper divisors (11104557).

21554643 is a wasteful number, since it uses less digits than its factorization.

21554643 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 323.

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

The square root of 21554643 is about 4642.6978148486. The cubic root of 21554643 is about 278.3002595750.

The spelling of 21554643 in words is "twenty-one million, five hundred fifty-four thousand, six hundred forty-three".