15515887121 has 4 divisors (see below), whose sum is σ = 17732442432. Its totient is φ = 13299331812.

The previous prime is 15515887061. The next prime is 15515887129. The reversal of 15515887121 is 12178851551.

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.

It is a cyclic number.

It is not a de Polignac number, because 15515887121 - 2¹⁴ = 15515870737 is a prime.

It is a super-2 number, since 2×15515887121² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (15515887129) 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, 1108277645 + ... + 1108277658.

It is an arithmetic number, because the mean of its divisors is an integer number (4433110608).

Almost surely, 2^15515887121 is an apocalyptic number.

It is an amenable number.

15515887121 is a deficient number, since it is larger than the sum of its proper divisors (2216555311).

15515887121 is an equidigital number, since it uses as much as digits as its factorization.

15515887121 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2216555310.

The product of its digits is 112000, while the sum is 44.

The spelling of 15515887121 in words is "fifteen billion, five hundred fifteen million, eight hundred eighty-seven thousand, one hundred twenty-one".