21155001651655 has 4 divisors (see below), whose sum is σ = 25386001981992. Its totient is φ = 16924001321320.

The previous prime is 21155001651653. The next prime is 21155001651677. The reversal of 21155001651655 is 55615610055112.

It is a semiprime because it is the product of two primes.

It is not a de Polignac number, because 21155001651655 - 2¹ = 21155001651653 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 (21155001651653) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2115500165161 + ... + 2115500165170.

It is an arithmetic number, because the mean of its divisors is an integer number (6346500495498).

Almost surely, 2^{21155001651655} is an apocalyptic number.

21155001651655 is a deficient number, since it is larger than the sum of its proper divisors (4231000330337).

21155001651655 is an equidigital number, since it uses as much as digits as its factorization.

21155001651655 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4231000330336.

The product of its (nonzero) digits is 225000, while the sum is 43.

The spelling of 21155001651655 in words is "twenty-one trillion, one hundred fifty-five billion, one million, six hundred fifty-one thousand, six hundred fifty-five".