157521991 has 4 divisors (see below), whose sum is σ = 171842184. Its totient is φ = 143201800.

The previous prime is 157521979. The next prime is 157522019. The reversal of 157521991 is 199125751.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 199125751 = 11 ⋅18102341.

It is a cyclic number.

It is not a de Polignac number, because 157521991 - 2¹³ = 157513799 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 (157521961) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 7160080 + ... + 7160101.

It is an arithmetic number, because the mean of its divisors is an integer number (42960546).

Almost surely, 2^157521991 is an apocalyptic number.

157521991 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

157521991 is a deficient number, since it is larger than the sum of its proper divisors (14320193).

157521991 is a wasteful number, since it uses less digits than its factorization.

157521991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 14320192.

The product of its digits is 28350, while the sum is 40.

The square root of 157521991 is about 12550.7765098419. The cubic root of 157521991 is about 540.0662824445.

The spelling of 157521991 in words is "one hundred fifty-seven million, five hundred twenty-one thousand, nine hundred ninety-one".