1538223721 has 8 divisors (see below), whose sum is σ = 1561843040. Its totient is φ = 1514623968.

The previous prime is 1538223719. The next prime is 1538223781. The reversal of 1538223721 is 1273228351.

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 1538223721 - 2¹ = 1538223719 is a prime.

It is a super-2 number, since 2×1538223721² = 4732264431694171682, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1538223781) 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, 268990 + ... + 274648.

It is an arithmetic number, because the mean of its divisors is an integer number (195230380).

Almost surely, 2^1538223721 is an apocalyptic number.

It is an amenable number.

1538223721 is a deficient number, since it is larger than the sum of its proper divisors (23619319).

1538223721 is an equidigital number, since it uses as much as digits as its factorization.

1538223721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9783.

The product of its digits is 20160, while the sum is 34.

The square root of 1538223721 is about 39220.1953207783. The cubic root of 1538223721 is about 1154.3561864880.

The spelling of 1538223721 in words is "one billion, five hundred thirty-eight million, two hundred twenty-three thousand, seven hundred twenty-one".