21257811 has 12 divisors (see below), whose sum is σ = 30820192. Its totient is φ = 14119056.

The previous prime is 21257809. The next prime is 21257843. The reversal of 21257811 is 11875212.

It is not a de Polignac number, because 21257811 - 2¹ = 21257809 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21257801) 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, 1771 + ... + 6756.

Almost surely, 2^21257811 is an apocalyptic number.

21257811 is a deficient number, since it is larger than the sum of its proper divisors (9562381).

21257811 is a wasteful number, since it uses less digits than its factorization.

21257811 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8810 (or 8807 counting only the distinct ones).

The product of its digits is 1120, while the sum is 27.

The square root of 21257811 is about 4610.6193727091. The cubic root of 21257811 is about 277.0168461475.

The spelling of 21257811 in words is "twenty-one million, two hundred fifty-seven thousand, eight hundred eleven".