21257005 has 16 divisors (see below), whose sum is σ = 31803264. Its totient is φ = 13250880.

The previous prime is 21257003. The next prime is 21257011. The reversal of 21257005 is 50075212.

It is not a de Polignac number, because 21257005 - 2¹ = 21257003 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21257003) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 27222 + ... + 27991.

It is an arithmetic number, because the mean of its divisors is an integer number (1987704).

Almost surely, 2^21257005 is an apocalyptic number.

It is an amenable number.

21257005 is a deficient number, since it is larger than the sum of its proper divisors (10546259).

21257005 is a wasteful number, since it uses less digits than its factorization.

21257005 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 55236.

The product of its (nonzero) digits is 700, while the sum is 22.

The square root of 21257005 is about 4610.5319649689. The cubic root of 21257005 is about 277.0133450282.

The spelling of 21257005 in words is "twenty-one million, two hundred fifty-seven thousand, five".