20249721 has 6 divisors (see below), whose sum is σ = 29249610. Its totient is φ = 13499808.

The previous prime is 20249717. The next prime is 20249731. The reversal of 20249721 is 12794202.

It can be written as a sum of positive squares in only one way, i.e., 16088121 + 4161600 = 4011^2 + 2040^2 .

It is not a de Polignac number, because 20249721 - 2² = 20249717 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20249731) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1124976 + ... + 1124993.

It is an arithmetic number, because the mean of its divisors is an integer number (4874935).

Almost surely, 2^20249721 is an apocalyptic number.

It is an amenable number.

20249721 is a deficient number, since it is larger than the sum of its proper divisors (8999889).

20249721 is a wasteful number, since it uses less digits than its factorization.

20249721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2249975 (or 2249972 counting only the distinct ones).

The product of its (nonzero) digits is 2016, while the sum is 27.

The square root of 20249721 is about 4499.9689998932. The cubic root of 20249721 is about 272.5668371249.

The spelling of 20249721 in words is "twenty million, two hundred forty-nine thousand, seven hundred twenty-one".