21236072721 has 8 divisors (see below), whose sum is σ = 28316131680. Its totient is φ = 14156697792.

The previous prime is 21236072659. The next prime is 21236072723. The reversal of 21236072721 is 12727063212.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21236072721 - 2⁶ = 21236072657 is a prime.

It is a super-2 number, since 2×21236072721² (a number of 21 digits) contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21236072723) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 93555 + ... + 226328.

It is an arithmetic number, because the mean of its divisors is an integer number (3539516460).

Almost surely, 2^21236072721 is an apocalyptic number.

It is an amenable number.

21236072721 is a deficient number, since it is larger than the sum of its proper divisors (7080058959).

21236072721 is a wasteful number, since it uses less digits than its factorization.

21236072721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 342015.

The product of its (nonzero) digits is 14112, while the sum is 33.

The spelling of 21236072721 in words is "twenty-one billion, two hundred thirty-six million, seventy-two thousand, seven hundred twenty-one".