151555721 has 4 divisors (see below), whose sum is σ = 155252244. Its totient is φ = 147859200.

The previous prime is 151555699. The next prime is 151555739. The reversal of 151555721 is 127555151.

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 1860496 + 149695225 = 1364^2 + 12235^2 .

It is a cyclic number.

It is not a de Polignac number, because 151555721 - 2¹⁴ = 151539337 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (151555741) 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, 1848200 + ... + 1848281.

It is an arithmetic number, because the mean of its divisors is an integer number (38813061).

Almost surely, 2^151555721 is an apocalyptic number.

It is an amenable number.

151555721 is a deficient number, since it is larger than the sum of its proper divisors (3696523).

151555721 is an equidigital number, since it uses as much as digits as its factorization.

151555721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3696522.

The product of its digits is 8750, while the sum is 32.

The square root of 151555721 is about 12310.7969279003. The cubic root of 151555721 is about 533.1598596840.

The spelling of 151555721 in words is "one hundred fifty-one million, five hundred fifty-five thousand, seven hundred twenty-one".