20147721 has 32 divisors (see below), whose sum is σ = 31190400. Its totient is φ = 11450880.

The previous prime is 20147717. The next prime is 20147723. The reversal of 20147721 is 12774102.

It is not a de Polignac number, because 20147721 - 2² = 20147717 is a prime.

It is a super-2 number, since 2×20147721² = 811861322987682, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 20147691 and 20147700.

It is not an unprimeable number, because it can be changed into a prime (20147723) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 35125 + ... + 35693.

It is an arithmetic number, because the mean of its divisors is an integer number (974700).

Almost surely, 2^20147721 is an apocalyptic number.

It is an amenable number.

20147721 is a deficient number, since it is larger than the sum of its proper divisors (11042679).

20147721 is a wasteful number, since it uses less digits than its factorization.

20147721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 649.

The product of its (nonzero) digits is 784, while the sum is 24.

The square root of 20147721 is about 4488.6212805270. The cubic root of 20147721 is about 272.1084171678.

It can be divided in two parts, 20 and 147721, that added together give a palindrome (147741).

The spelling of 20147721 in words is "twenty million, one hundred forty-seven thousand, seven hundred twenty-one".