21154560222665 has 16 divisors (see below), whose sum is σ = 26354288353680. Its totient is φ = 16281924341760.

The previous prime is 21154560222661. The next prime is 21154560222713. The reversal of 21154560222665 is 56622206545112.

It can be written as a sum of positive squares in 8 ways, for example, as 9976613689 + 21144583608976 = 99883^2 + 4598324^2 .

It is not a de Polignac number, because 21154560222665 - 2² = 21154560222661 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21154560222661) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 259556264 + ... + 259637753.

It is an arithmetic number, because the mean of its divisors is an integer number (1647143022105).

Almost surely, 2^{21154560222665} is an apocalyptic number.

It is an amenable number.

21154560222665 is a deficient number, since it is larger than the sum of its proper divisors (5199728131015).

21154560222665 is a wasteful number, since it uses less digits than its factorization.

21154560222665 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 519194332.

The product of its (nonzero) digits is 1728000, while the sum is 47.

Adding to 21154560222665 its reverse (56622206545112), we get a palindrome (77776766767777).

The spelling of 21154560222665 in words is "twenty-one trillion, one hundred fifty-four billion, five hundred sixty million, two hundred twenty-two thousand, six hundred sixty-five".