21154661365655 has 8 divisors (see below), whose sum is σ = 25505904510384. Its totient is φ = 16843521844800.

The previous prime is 21154661365597. The next prime is 21154661365679. The reversal of 21154661365655 is 55656316645112.

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

It is not a de Polignac number, because 21154661365655 - 2¹⁶ = 21154661300119 is a prime.

It is a super-2 number, since 2×21154661365655² (a number of 27 digits) contains 22 as substring.

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 21154661365655.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 10025904806 + ... + 10025906915.

It is an arithmetic number, because the mean of its divisors is an integer number (3188238063798).

Almost surely, 2^{21154661365655} is an apocalyptic number.

21154661365655 is a deficient number, since it is larger than the sum of its proper divisors (4351243144729).

21154661365655 is a wasteful number, since it uses less digits than its factorization.

21154661365655 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 20051811937.

The product of its digits is 19440000, while the sum is 56.

The spelling of 21154661365655 in words is "twenty-one trillion, one hundred fifty-four billion, six hundred sixty-one million, three hundred sixty-five thousand, six hundred fifty-five".