20723681 has 4 divisors (see below), whose sum is σ = 22607664. Its totient is φ = 18839700.

The previous prime is 20723671. The next prime is 20723683. The reversal of 20723681 is 18632702.

It is a happy number.

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 not a de Polignac number, because 20723681 - 2⁶ = 20723617 is a prime.

It is a super-2 number, since 2×20723681² = 858941908379522, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20723683) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 941975 + ... + 941996.

It is an arithmetic number, because the mean of its divisors is an integer number (5651916).

Almost surely, 2^20723681 is an apocalyptic number.

It is an amenable number.

20723681 is a deficient number, since it is larger than the sum of its proper divisors (1883983).

20723681 is a wasteful number, since it uses less digits than its factorization.

20723681 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1883982.

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

The square root of 20723681 is about 4552.3269873769. The cubic root of 20723681 is about 274.6770025946.

The spelling of 20723681 in words is "twenty million, seven hundred twenty-three thousand, six hundred eighty-one".