20721449 has 16 divisors (see below), whose sum is σ = 24330240. Its totient is φ = 17281680.

The previous prime is 20721439. The next prime is 20721461. The reversal of 20721449 is 94412702.

It is a cyclic number.

It is not a de Polignac number, because 20721449 - 2⁴ = 20721433 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (20721439) by changing a digit.

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 in 15 ways as a sum of consecutive naturals, for example, 53912 + ... + 54294.

It is an arithmetic number, because the mean of its divisors is an integer number (1520640).

Almost surely, 2^20721449 is an apocalyptic number.

It is an amenable number.

20721449 is a deficient number, since it is larger than the sum of its proper divisors (3608791).

20721449 is a wasteful number, since it uses less digits than its factorization.

20721449 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 580.

The product of its (nonzero) digits is 4032, while the sum is 29.

The square root of 20721449 is about 4552.0818314261. The cubic root of 20721449 is about 274.6671410731.

The spelling of 20721449 in words is "twenty million, seven hundred twenty-one thousand, four hundred forty-nine".