21573857 has 2 divisors, whose sum is σ = 21573858. Its totient is φ = 21573856.

The previous prime is 21573829. The next prime is 21573863. The reversal of 21573857 is 75837512.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 17230801 + 4343056 = 4151^2 + 2084^2 .

It is a cyclic number.

It is not a de Polignac number, because 21573857 - 2¹⁶ = 21508321 is a prime.

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 21573857.

It is not a weakly prime, because it can be changed into another prime (21573887) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10786928 + 10786929.

It is an arithmetic number, because the mean of its divisors is an integer number (10786929).

Almost surely, 2^21573857 is an apocalyptic number.

It is an amenable number.

21573857 is a deficient number, since it is larger than the sum of its proper divisors (1).

21573857 is an equidigital number, since it uses as much as digits as its factorization.

21573857 is an evil number, because the sum of its binary digits is even.

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

The square root of 21573857 is about 4644.7666249232. The cubic root of 21573857 is about 278.3829281228.

The spelling of 21573857 in words is "twenty-one million, five hundred seventy-three thousand, eight hundred fifty-seven".