21039985 has 8 divisors (see below), whose sum is σ = 25272936. Its totient is φ = 16815360.

The previous prime is 21039971. The next prime is 21039989. The reversal of 21039985 is 58993012.

It can be written as a sum of positive squares in 4 ways, for example, as 1361889 + 19678096 = 1167^2 + 4436^2 .

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

It is not a de Polignac number, because 21039985 - 2¹³ = 21031793 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21039989) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 7497 + ... + 9913.

It is an arithmetic number, because the mean of its divisors is an integer number (3159117).

Almost surely, 2^21039985 is an apocalyptic number.

It is an amenable number.

21039985 is a deficient number, since it is larger than the sum of its proper divisors (4232951).

21039985 is a wasteful number, since it uses less digits than its factorization.

21039985 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4163.

The product of its (nonzero) digits is 19440, while the sum is 37.

The square root of 21039985 is about 4586.9363413939. The cubic root of 21039985 is about 276.0674107203.

The spelling of 21039985 in words is "twenty-one million, thirty-nine thousand, nine hundred eighty-five".