21409994 has 4 divisors (see below), whose sum is σ = 32114994. Its totient is φ = 10704996.

The previous prime is 21409991. The next prime is 21410003. The reversal of 21409994 is 49990412.

It is a happy number.

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., 13213225 + 8196769 = 3635^2 + 2863^2 .

It is not an unprimeable number, because it can be changed into a prime (21409991) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5352497 + ... + 5352500.

Almost surely, 2^21409994 is an apocalyptic number.

21409994 is a deficient number, since it is larger than the sum of its proper divisors (10705000).

21409994 is a wasteful number, since it uses less digits than its factorization.

21409994 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10704999.

The product of its (nonzero) digits is 23328, while the sum is 38.

The square root of 21409994 is about 4627.0934721486. The cubic root of 21409994 is about 277.6763222141.

The spelling of 21409994 in words is "twenty-one million, four hundred nine thousand, nine hundred ninety-four".