21031385 has 16 divisors (see below), whose sum is σ = 26827200. Its totient is φ = 15782976.

The previous prime is 21031379. The next prime is 21031391. The reversal of 21031385 is 58313012.

It is an interprime number because it is at equal distance from previous prime (21031379) and next prime (21031391).

It is a cyclic number.

It is not a de Polignac number, because 21031385 - 2¹⁶ = 20965849 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21031385.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 9131 + ... + 11199.

It is an arithmetic number, because the mean of its divisors is an integer number (1676700).

Almost surely, 2^21031385 is an apocalyptic number.

It is an amenable number.

21031385 is a deficient number, since it is larger than the sum of its proper divisors (5795815).

21031385 is a wasteful number, since it uses less digits than its factorization.

21031385 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2200.

The product of its (nonzero) digits is 720, while the sum is 23.

The square root of 21031385 is about 4585.9988006976. The cubic root of 21031385 is about 276.0297918202.

Adding to 21031385 its reverse (58313012), we get a palindrome (79344397).

The spelling of 21031385 in words is "twenty-one million, thirty-one thousand, three hundred eighty-five".