21010257 has 12 divisors (see below), whose sum is σ = 31945680. Its totient is φ = 13269528.

The previous prime is 21010237. The next prime is 21010259. The reversal of 21010257 is 75201012.

It is not a de Polignac number, because 21010257 - 2⁶ = 21010193 is a prime.

It is a super-3 number, since 3×21010257³ (a number of 23 digits) contains 333 as substring.

It is not an unprimeable number, because it can be changed into a prime (21010259) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 61263 + ... + 61604.

It is an arithmetic number, because the mean of its divisors is an integer number (2662140).

Almost surely, 2^21010257 is an apocalyptic number.

It is an amenable number.

21010257 is a deficient number, since it is larger than the sum of its proper divisors (10935423).

21010257 is a wasteful number, since it uses less digits than its factorization.

21010257 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 122892 (or 122889 counting only the distinct ones).

The product of its (nonzero) digits is 140, while the sum is 18.

The square root of 21010257 is about 4583.6946887855. The cubic root of 21010257 is about 275.9373282402.

Adding to 21010257 its reverse (75201012), we get a palindrome (96211269).

The spelling of 21010257 in words is "twenty-one million, ten thousand, two hundred fifty-seven".