20994721 has 4 divisors (see below), whose sum is σ = 22903344. Its totient is φ = 19086100.

The previous prime is 20994713. The next prime is 20994749. The reversal of 20994721 is 12749902.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 20994721 - 2³ = 20994713 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20994821) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 954295 + ... + 954316.

It is an arithmetic number, because the mean of its divisors is an integer number (5725836).

Almost surely, 2^20994721 is an apocalyptic number.

It is an amenable number.

20994721 is a deficient number, since it is larger than the sum of its proper divisors (1908623).

20994721 is a wasteful number, since it uses less digits than its factorization.

20994721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1908622.

The product of its (nonzero) digits is 9072, while the sum is 34.

The square root of 20994721 is about 4581.9996726320. Note that the first 3 decimals coincide. The cubic root of 20994721 is about 275.8692976678.

The spelling of 20994721 in words is "twenty million, nine hundred ninety-four thousand, seven hundred twenty-one".