21554257 has 2 divisors, whose sum is σ = 21554258. Its totient is φ = 21554256.

The previous prime is 21554237. The next prime is 21554297. The reversal of 21554257 is 75245512.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 21538881 + 15376 = 4641^2 + 124^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21554257 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21554237) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10777128 + 10777129.

It is an arithmetic number, because the mean of its divisors is an integer number (10777129).

Almost surely, 2^21554257 is an apocalyptic number.

It is an amenable number.

21554257 is a deficient number, since it is larger than the sum of its proper divisors (1).

21554257 is an equidigital number, since it uses as much as digits as its factorization.

21554257 is an evil number, because the sum of its binary digits is even.

The product of its digits is 14000, while the sum is 31.

The square root of 21554257 is about 4642.6562440051. The cubic root of 21554257 is about 278.2985983004.

Adding to 21554257 its reverse (75245512), we get a palindrome (96799769).

The spelling of 21554257 in words is "twenty-one million, five hundred fifty-four thousand, two hundred fifty-seven".