21990002 has 4 divisors (see below), whose sum is σ = 32985006. Its totient is φ = 10995000.

The previous prime is 21989999. The next prime is 21990013. The reversal of 21990002 is 20009912.

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., 11498881 + 10491121 = 3391^2 + 3239^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 21990002.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5497499 + ... + 5497502.

Almost surely, 2^21990002 is an apocalyptic number.

21990002 is a deficient number, since it is larger than the sum of its proper divisors (10995004).

21990002 is a wasteful number, since it uses less digits than its factorization.

21990002 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10995003.

The product of its (nonzero) digits is 324, while the sum is 23.

The square root of 21990002 is about 4689.3498483265. The cubic root of 21990002 is about 280.1614799835.

Adding to 21990002 its reverse (20009912), we get a palindrome (41999914).

The spelling of 21990002 in words is "twenty-one million, nine hundred ninety thousand, two".