21138677961 has 16 divisors (see below), whose sum is σ = 28531481664. Its totient is φ = 13919246784.

The previous prime is 21138677957. The next prime is 21138678047. The reversal of 21138677961 is 16977683112.

It is a happy number.

It is not a de Polignac number, because 21138677961 - 2² = 21138677957 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21138677921) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1376055 + ... + 1391331.

It is an arithmetic number, because the mean of its divisors is an integer number (1783217604).

Almost surely, 2^21138677961 is an apocalyptic number.

It is an amenable number.

21138677961 is a deficient number, since it is larger than the sum of its proper divisors (7392803703).

21138677961 is a wasteful number, since it uses less digits than its factorization.

21138677961 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 20920.

The product of its digits is 762048, while the sum is 51.

The spelling of 21138677961 in words is "twenty-one billion, one hundred thirty-eight million, six hundred seventy-seven thousand, nine hundred sixty-one".