21554881 has 2 divisors, whose sum is σ = 21554882. Its totient is φ = 21554880.

The previous prime is 21554849. The next prime is 21554891. The reversal of 21554881 is 18845512.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 21529600 + 25281 = 4640^2 + 159^2 .

It is a cyclic number.

It is not a de Polignac number, because 21554881 - 2⁵ = 21554849 is a prime.

It is a super-2 number, since 2×21554881² = 929225789848322, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21554891) by changing a digit.

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 as a sum of consecutive naturals, namely, 10777440 + 10777441.

It is an arithmetic number, because the mean of its divisors is an integer number (10777441).

Almost surely, 2^21554881 is an apocalyptic number.

It is an amenable number.

21554881 is a deficient number, since it is larger than the sum of its proper divisors (1).

21554881 is an equidigital number, since it uses as much as digits as its factorization.

21554881 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 12800, while the sum is 34.

The square root of 21554881 is about 4642.7234464267. The cubic root of 21554881 is about 278.3012838743.

The spelling of 21554881 in words is "twenty-one million, five hundred fifty-four thousand, eight hundred eighty-one".