21215994 has 16 divisors (see below), whose sum is σ = 43895520. Its totient is φ = 6828080.

The previous prime is 21215993. The next prime is 21216001. The reversal of 21215994 is 49951212.

It is a Smith number, since the sum of its digits (33) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is not an unprimeable number, because it can be changed into a prime (21215993) 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, 60792 + ... + 61139.

It is an arithmetic number, because the mean of its divisors is an integer number (2743470).

Almost surely, 2^21215994 is an apocalyptic number.

21215994 is an abundant number, since it is smaller than the sum of its proper divisors (22679526).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21215994 is a wasteful number, since it uses less digits than its factorization.

21215994 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 121965.

The product of its digits is 6480, while the sum is 33.

The square root of 21215994 is about 4606.0822832425. The cubic root of 21215994 is about 276.8350836644.

The spelling of 21215994 in words is "twenty-one million, two hundred fifteen thousand, nine hundred ninety-four".