15663506221 has 8 divisors (see below), whose sum is σ = 17124372864. Its totient is φ = 14208791520.

The previous prime is 15663506219. The next prime is 15663506227. The reversal of 15663506221 is 12260536651.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 15663506221 - 2¹ = 15663506219 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (15663506227) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1532656 + ... + 1542841.

It is an arithmetic number, because the mean of its divisors is an integer number (2140546608).

Almost surely, 2^15663506221 is an apocalyptic number.

15663506221 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

15663506221 is a deficient number, since it is larger than the sum of its proper divisors (1460866643).

15663506221 is a wasteful number, since it uses less digits than its factorization.

15663506221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3075971.

The product of its (nonzero) digits is 64800, while the sum is 37.

The spelling of 15663506221 in words is "fifteen billion, six hundred sixty-three million, five hundred six thousand, two hundred twenty-one".