15121221621 has 16 divisors (see below), whose sum is σ = 22030768128. Its totient is φ = 9149266800.

The previous prime is 15121221617. The next prime is 15121221623. The reversal of 15121221621 is 12612212151.

It is a happy number.

It is not a de Polignac number, because 15121221621 - 2² = 15121221617 is a prime.

It is a super-2 number, since 2×15121221621² (a number of 21 digits) contains 22 as substring.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 15121221591 and 15121221600.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (15121221623) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 357415 + ... + 397476.

It is an arithmetic number, because the mean of its divisors is an integer number (1376923008).

Almost surely, 2^15121221621 is an apocalyptic number.

15121221621 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

15121221621 is a deficient number, since it is larger than the sum of its proper divisors (6909546507).

15121221621 is a wasteful number, since it uses less digits than its factorization.

15121221621 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 755512.

The product of its digits is 480, while the sum is 24.

Adding to 15121221621 its reverse (12612212151), we get a palindrome (27733433772).

The spelling of 15121221621 in words is "fifteen billion, one hundred twenty-one million, two hundred twenty-one thousand, six hundred twenty-one".