21155165256145 has 16 divisors (see below), whose sum is σ = 25542933232320. Its totient is φ = 16819650316224.

The previous prime is 21155165256107. The next prime is 21155165256187. The reversal of 21155165256145 is 54165256155112.

It is a cyclic number.

It is not a de Polignac number, because 21155165256145 - 2¹⁵ = 21155165223377 is a prime.

It is a super-2 number, since 2×21155165256145² (a number of 27 digits) contains 22 as substring.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 21073567 + ... + 22054603.

It is an arithmetic number, because the mean of its divisors is an integer number (1596433327020).

Almost surely, 2^{21155165256145} is an apocalyptic number.

It is an amenable number.

21155165256145 is a deficient number, since it is larger than the sum of its proper divisors (4387767976175).

21155165256145 is a wasteful number, since it uses less digits than its factorization.

21155165256145 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1007664.

The product of its digits is 1800000, while the sum is 49.

The spelling of 21155165256145 in words is "twenty-one trillion, one hundred fifty-five billion, one hundred sixty-five million, two hundred fifty-six thousand, one hundred forty-five".