20701721 has 4 divisors (see below), whose sum is σ = 20719872. Its totient is φ = 20683572.

The previous prime is 20701717. The next prime is 20701739. The reversal of 20701721 is 12710702.

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 a cyclic number.

It is not a de Polignac number, because 20701721 - 2² = 20701717 is a prime.

It is a super-2 number, since 2×20701721² = 857122504723682, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 20701693 and 20701702.

It is not an unprimeable number, because it can be changed into a prime (20701711) 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 3 ways as a sum of consecutive naturals, for example, 7241 + ... + 9686.

It is an arithmetic number, because the mean of its divisors is an integer number (5179968).

Almost surely, 2^20701721 is an apocalyptic number.

It is an amenable number.

20701721 is a deficient number, since it is larger than the sum of its proper divisors (18151).

20701721 is a wasteful number, since it uses less digits than its factorization.

20701721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 18150.

The product of its (nonzero) digits is 196, while the sum is 20.

The square root of 20701721 is about 4549.9143947991. The cubic root of 20701721 is about 274.5799471404.

The spelling of 20701721 in words is "twenty million, seven hundred one thousand, seven hundred twenty-one".