1557783921 has 16 divisors (see below), whose sum is σ = 2090990720. Its totient is φ = 1031564160.

The previous prime is 1557783911. The next prime is 1557783937. The reversal of 1557783921 is 1293877551.

It is not a de Polignac number, because 1557783921 - 2¹³ = 1557775729 is a prime.

It is a super-2 number, since 2×1557783921² = 4853381489052268482, which contains 22 as substring.

It is a Smith number, since the sum of its digits (48) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1557783911) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 872796 + ... + 874578.

It is an arithmetic number, because the mean of its divisors is an integer number (130686920).

Almost surely, 2^1557783921 is an apocalyptic number.

It is an amenable number.

1557783921 is a deficient number, since it is larger than the sum of its proper divisors (533206799).

1557783921 is a wasteful number, since it uses less digits than its factorization.

1557783921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3576.

The product of its digits is 529200, while the sum is 48.

The square root of 1557783921 is about 39468.7714655524. The cubic root of 1557783921 is about 1159.2285598598.

The spelling of 1557783921 in words is "one billion, five hundred fifty-seven million, seven hundred eighty-three thousand, nine hundred twenty-one".