21215986 has 8 divisors (see below), whose sum is σ = 34717104. Its totient is φ = 9643620.

The previous prime is 21215977. The next prime is 21215993. The reversal of 21215986 is 68951212.

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

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 482160 + ... + 482203.

It is an arithmetic number, because the mean of its divisors is an integer number (4339638).

Almost surely, 2^21215986 is an apocalyptic number.

21215986 is a deficient number, since it is larger than the sum of its proper divisors (13501118).

21215986 is a wasteful number, since it uses less digits than its factorization.

21215986 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 964376.

The product of its digits is 8640, while the sum is 34.

The square root of 21215986 is about 4606.0814148254. The cubic root of 21215986 is about 276.8350488686.

It can be divided in two parts, 21215 and 986, that added together give a square (22201 = 149²).

The spelling of 21215986 in words is "twenty-one million, two hundred fifteen thousand, nine hundred eighty-six".