21002685 has 16 divisors (see below), whose sum is σ = 36659520. Its totient is φ = 10183040.

The previous prime is 21002677. The next prime is 21002689. The reversal of 21002685 is 58620012.

It is not a de Polignac number, because 21002685 - 2³ = 21002677 is a prime.

It is a super-2 number, since 2×21002685² = 882225554418450, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21002689) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 63480 + ... + 63809.

It is an arithmetic number, because the mean of its divisors is an integer number (2291220).

Almost surely, 2^21002685 is an apocalyptic number.

It is an amenable number.

21002685 is a deficient number, since it is larger than the sum of its proper divisors (15656835).

21002685 is a wasteful number, since it uses less digits than its factorization.

21002685 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 127308.

The product of its (nonzero) digits is 960, while the sum is 24.

The square root of 21002685 is about 4582.8686431099. The cubic root of 21002685 is about 275.9041754091.

Adding to 21002685 its reverse (58620012), we get a palindrome (79622697).

The spelling of 21002685 in words is "twenty-one million, two thousand, six hundred eighty-five".