21155651649 has 24 divisors (see below), whose sum is σ = 35297132832. Its totient is φ = 12067393920.

The previous prime is 21155651599. The next prime is 21155651659. The reversal of 21155651649 is 94615655112.

21155651649 is a `hidden beast` number, since 2 + 1 + 1 + 556 + 51 + 6 + 49 = 666.

It is not a de Polignac number, because 21155651649 - 2⁸ = 21155651393 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21155651659) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 6283419 + ... + 6286784.

It is an arithmetic number, because the mean of its divisors is an integer number (1470713868).

Almost surely, 2^21155651649 is an apocalyptic number.

It is an amenable number.

21155651649 is a deficient number, since it is larger than the sum of its proper divisors (14141481183).

21155651649 is a wasteful number, since it uses less digits than its factorization.

21155651649 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12570237 (or 12570234 counting only the distinct ones).

The product of its digits is 324000, while the sum is 45.

The spelling of 21155651649 in words is "twenty-one billion, one hundred fifty-five million, six hundred fifty-one thousand, six hundred forty-nine".