20472721921 has 8 divisors (see below), whose sum is σ = 20981626344. Its totient is φ = 19964273280.

The previous prime is 20472721897. The next prime is 20472721943. The reversal of 20472721921 is 12912727402.

It can be written as a sum of positive squares in 4 ways, for example, as 10294131600 + 10178590321 = 101460^2 + 100889^2 .

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

It is a cyclic number.

It is not a de Polignac number, because 20472721921 - 2⁷ = 20472721793 is a prime.

It is not an unprimeable number, because it can be changed into a prime (20472721961) 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, 22086 + ... + 203551.

It is an arithmetic number, because the mean of its divisors is an integer number (2622703293).

Almost surely, 2^20472721921 is an apocalyptic number.

It is an amenable number.

20472721921 is a deficient number, since it is larger than the sum of its proper divisors (508904423).

20472721921 is a wasteful number, since it uses less digits than its factorization.

20472721921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 227891.

The product of its (nonzero) digits is 28224, while the sum is 37.

The spelling of 20472721921 in words is "twenty billion, four hundred seventy-two million, seven hundred twenty-one thousand, nine hundred twenty-one".