21155631385 has 16 divisors (see below), whose sum is σ = 30720110976. Its totient is φ = 13653381888.

The previous prime is 21155631359. The next prime is 21155631407. The reversal of 21155631385 is 58313655112.

It is a cyclic number.

It is not a de Polignac number, because 21155631385 - 2⁵ = 21155631353 is a prime.

It is a Duffinian number.

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, 17777247 + ... + 17778436.

It is an arithmetic number, because the mean of its divisors is an integer number (1920006936).

Almost surely, 2^21155631385 is an apocalyptic number.

It is an amenable number.

21155631385 is a deficient number, since it is larger than the sum of its proper divisors (9564479591).

21155631385 is a wasteful number, since it uses less digits than its factorization.

21155631385 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 35555712.

The product of its digits is 108000, while the sum is 40.

The spelling of 21155631385 in words is "twenty-one billion, one hundred fifty-five million, six hundred thirty-one thousand, three hundred eighty-five".