20195721 has 24 divisors (see below), whose sum is σ = 35904960. Its totient is φ = 10652256.

The previous prime is 20195719. The next prime is 20195723. The reversal of 20195721 is 12759102.

It is an interprime number because it is at equal distance from previous prime (20195719) and next prime (20195723).

It is not a de Polignac number, because 20195721 - 2¹ = 20195719 is a prime.

It is not an unprimeable number, because it can be changed into a prime (20195723) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 11511 + ... + 13148.

It is an arithmetic number, because the mean of its divisors is an integer number (1496040).

Almost surely, 2^20195721 is an apocalyptic number.

20195721 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

It is an amenable number.

20195721 is a deficient number, since it is larger than the sum of its proper divisors (15709239).

20195721 is a wasteful number, since it uses less digits than its factorization.

20195721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 24685 (or 24682 counting only the distinct ones).

The product of its (nonzero) digits is 1260, while the sum is 27.

The square root of 20195721 is about 4493.9649531344. The cubic root of 20195721 is about 272.3243364667.

The spelling of 20195721 in words is "twenty million, one hundred ninety-five thousand, seven hundred twenty-one".