21553787 has 2 divisors, whose sum is σ = 21553788. Its totient is φ = 21553786.

The previous prime is 21553717. The next prime is 21553789. The reversal of 21553787 is 78735512.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21553787 - 2⁸ = 21553531 is a prime.

Together with 21553789, it forms a pair of twin primes.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21553787.

It is not a weakly prime, because it can be changed into another prime (21553789) 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, 10776893 + 10776894.

It is an arithmetic number, because the mean of its divisors is an integer number (10776894).

Almost surely, 2^21553787 is an apocalyptic number.

21553787 is a deficient number, since it is larger than the sum of its proper divisors (1).

21553787 is an equidigital number, since it uses as much as digits as its factorization.

21553787 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 58800, while the sum is 38.

The square root of 21553787 is about 4642.6056261543. The cubic root of 21553787 is about 278.2965754782.

The spelling of 21553787 in words is "twenty-one million, five hundred fifty-three thousand, seven hundred eighty-seven".