21085851 has 8 divisors (see below), whose sum is σ = 28387840. Its totient is φ = 13920552.

The previous prime is 21085847. The next prime is 21085853. The reversal of 21085851 is 15858012.

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

It is not a de Polignac number, because 21085851 - 2² = 21085847 is a prime.

It is a super-2 number, since 2×21085851² = 889226224788402, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21085853) 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, 33811 + ... + 34428.

It is an arithmetic number, because the mean of its divisors is an integer number (3548480).

Almost surely, 2^21085851 is an apocalyptic number.

21085851 is a deficient number, since it is larger than the sum of its proper divisors (7301989).

21085851 is a wasteful number, since it uses less digits than its factorization.

21085851 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 68345.

The product of its (nonzero) digits is 3200, while the sum is 30.

The square root of 21085851 is about 4591.9332529992. The cubic root of 21085851 is about 276.2678690079.

The spelling of 21085851 in words is "twenty-one million, eighty-five thousand, eight hundred fifty-one".