21257018 has 8 divisors (see below), whose sum is σ = 32747412. Its totient is φ = 10341216.

The previous prime is 21257017. The next prime is 21257053. The reversal of 21257018 is 81075212.

It can be written as a sum of positive squares in 2 ways, for example, as 21132409 + 124609 = 4597^2 + 353^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is not an unprimeable number, because it can be changed into a prime (21257011) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 143555 + ... + 143702.

Almost surely, 2^21257018 is an apocalyptic number.

21257018 is a deficient number, since it is larger than the sum of its proper divisors (11490394).

21257018 is a wasteful number, since it uses less digits than its factorization.

21257018 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 287296.

The product of its (nonzero) digits is 1120, while the sum is 26.

The square root of 21257018 is about 4610.5333747843. The cubic root of 21257018 is about 277.0134014986.

The spelling of 21257018 in words is "twenty-one million, two hundred fifty-seven thousand, eighteen".