238721991 has 16 divisors (see below), whose sum is σ = 334139904. Its totient is φ = 151309664.

The previous prime is 238721983. The next prime is 238721999. The reversal of 238721991 is 199127832.

It is an interprime number because it is at equal distance from previous prime (238721983) and next prime (238721999).

It is a cyclic number.

It is not a de Polignac number, because 238721991 - 2³ = 238721983 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (238721999) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1165 + ... + 21881.

It is an arithmetic number, because the mean of its divisors is an integer number (20883744).

Almost surely, 2^238721991 is an apocalyptic number.

238721991 is a deficient number, since it is larger than the sum of its proper divisors (95417913).

238721991 is a wasteful number, since it uses less digits than its factorization.

238721991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 20910.

The product of its digits is 54432, while the sum is 42.

The square root of 238721991 is about 15450.6307638232. The cubic root of 238721991 is about 620.3414620976.

The spelling of 238721991 in words is "two hundred thirty-eight million, seven hundred twenty-one thousand, nine hundred ninety-one".