21642553 has 2 divisors, whose sum is σ = 21642554. Its totient is φ = 21642552.

The previous prime is 21642527. The next prime is 21642559. The reversal of 21642553 is 35524612.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 14417209 + 7225344 = 3797^2 + 2688^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21642553 is a prime.

It is not a weakly prime, because it can be changed into another prime (21642559) 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 as a sum of consecutive naturals, namely, 10821276 + 10821277.

It is an arithmetic number, because the mean of its divisors is an integer number (10821277).

Almost surely, 2^21642553 is an apocalyptic number.

It is an amenable number.

21642553 is a deficient number, since it is larger than the sum of its proper divisors (1).

21642553 is an equidigital number, since it uses as much as digits as its factorization.

21642553 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 7200, while the sum is 28.

The square root of 21642553 is about 4652.1557368601. The cubic root of 21642553 is about 278.6780929499.

The spelling of 21642553 in words is "twenty-one million, six hundred forty-two thousand, five hundred fifty-three".