151515721 has 4 divisors (see below), whose sum is σ = 173160832. Its totient is φ = 129870612.

The previous prime is 151515701. The next prime is 151515737. The reversal of 151515721 is 127515151.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 127515151 = 23 ⋅5544137.

It is a cyclic number.

It is not a de Polignac number, because 151515721 - 2¹³ = 151507529 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 151515721.

It is not an unprimeable number, because it can be changed into a prime (151515701) 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, 10822545 + ... + 10822558.

It is an arithmetic number, because the mean of its divisors is an integer number (43290208).

Almost surely, 2^151515721 is an apocalyptic number.

It is an amenable number.

151515721 is a deficient number, since it is larger than the sum of its proper divisors (21645111).

151515721 is an equidigital number, since it uses as much as digits as its factorization.

151515721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 21645110.

The product of its digits is 1750, while the sum is 28.

The square root of 151515721 is about 12309.1722304954. The cubic root of 151515721 is about 533.1129500485.

The spelling of 151515721 in words is "one hundred fifty-one million, five hundred fifteen thousand, seven hundred twenty-one".