21554543 has 2 divisors, whose sum is σ = 21554544. Its totient is φ = 21554542.

The previous prime is 21554539. The next prime is 21554557. The reversal of 21554543 is 34545512.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21554543 - 2² = 21554539 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21554513) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10777271 + 10777272.

It is an arithmetic number, because the mean of its divisors is an integer number (10777272).

Almost surely, 2^21554543 is an apocalyptic number.

21554543 is a deficient number, since it is larger than the sum of its proper divisors (1).

21554543 is an equidigital number, since it uses as much as digits as its factorization.

21554543 is an evil number, because the sum of its binary digits is even.

The product of its digits is 12000, while the sum is 29.

The square root of 21554543 is about 4642.6870452358. The cubic root of 21554543 is about 278.2998291949.

The spelling of 21554543 in words is "twenty-one million, five hundred fifty-four thousand, five hundred forty-three".