21151051555 has 8 divisors (see below), whose sum is σ = 25386145344. Its totient is φ = 16917585600.

The previous prime is 21151051549. The next prime is 21151051627. The reversal of 21151051555 is 55515015112.

It is a happy number.

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

It is not a de Polignac number, because 21151051555 - 2³¹ = 19003567907 is a prime.

It is a Duffinian 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, 378186 + ... + 430495.

It is an arithmetic number, because the mean of its divisors is an integer number (3173268168).

Almost surely, 2^21151051555 is an apocalyptic number.

21151051555 is a deficient number, since it is larger than the sum of its proper divisors (4235093789).

21151051555 is an equidigital number, since it uses as much as digits as its factorization.

21151051555 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 813917.

The product of its (nonzero) digits is 6250, while the sum is 31.

Adding to 21151051555 its reverse (55515015112), we get a palindrome (76666066667).

The spelling of 21151051555 in words is "twenty-one billion, one hundred fifty-one million, fifty-one thousand, five hundred fifty-five".