1581421901 has 4 divisors (see below), whose sum is σ = 1585662012. Its totient is φ = 1577181792.

The previous prime is 1581421859. The next prime is 1581421931. The reversal of 1581421901 is 1091241851.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 1365302500 + 216119401 = 36950^2 + 14701^2 .

It is a cyclic number.

It is not a de Polignac number, because 1581421901 - 2¹⁴ = 1581405517 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1581421931) 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, 2119496 + ... + 2120241.

It is an arithmetic number, because the mean of its divisors is an integer number (396415503).

Almost surely, 2^1581421901 is an apocalyptic number.

It is an amenable number.

1581421901 is a deficient number, since it is larger than the sum of its proper divisors (4240111).

1581421901 is an equidigital number, since it uses as much as digits as its factorization.

1581421901 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4240110.

The product of its (nonzero) digits is 2880, while the sum is 32.

The square root of 1581421901 is about 39767.0957073810. The cubic root of 1581421901 is about 1165.0625694136.

The spelling of 1581421901 in words is "one billion, five hundred eighty-one million, four hundred twenty-one thousand, nine hundred one".