21385057 has 2 divisors, whose sum is σ = 21385058. Its totient is φ = 21385056.

The previous prime is 21384991. The next prime is 21385069. The reversal of 21385057 is 75058312.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 21150801 + 234256 = 4599^2 + 484^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21385057 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21385087) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10692528 + 10692529.

It is an arithmetic number, because the mean of its divisors is an integer number (10692529).

Almost surely, 2^21385057 is an apocalyptic number.

It is an amenable number.

21385057 is a deficient number, since it is larger than the sum of its proper divisors (1).

21385057 is an equidigital number, since it uses as much as digits as its factorization.

21385057 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 8400, while the sum is 31.

The square root of 21385057 is about 4624.3980148772. The cubic root of 21385057 is about 277.5684737554.

The spelling of 21385057 in words is "twenty-one million, three hundred eighty-five thousand, fifty-seven".