21285986 has 4 divisors (see below), whose sum is σ = 31928982. Its totient is φ = 10642992.

The previous prime is 21285977. The next prime is 21286003. The reversal of 21285986 is 68958212.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in only one way, i.e., 16362025 + 4923961 = 4045^2 + 2219^2 .

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5321495 + ... + 5321498.

Almost surely, 2^21285986 is an apocalyptic number.

21285986 is a deficient number, since it is larger than the sum of its proper divisors (10642996).

21285986 is a wasteful number, since it uses less digits than its factorization.

21285986 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10642995.

The product of its digits is 69120, while the sum is 41.

The square root of 21285986 is about 4613.6738072820. The cubic root of 21285986 is about 277.1391777141.

The spelling of 21285986 in words is "twenty-one million, two hundred eighty-five thousand, nine hundred eighty-six".