21123936651 has 4 divisors (see below), whose sum is σ = 28165248872. Its totient is φ = 14082624432.

The previous prime is 21123936649. The next prime is 21123936689. The reversal of 21123936651 is 15663932112.

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

It is not a de Polignac number, because 21123936651 - 2¹ = 21123936649 is a prime.

It is a super-2 number, since 2×21123936651² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21123936751) 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, 3520656106 + ... + 3520656111.

It is an arithmetic number, because the mean of its divisors is an integer number (7041312218).

Almost surely, 2^21123936651 is an apocalyptic number.

21123936651 is a deficient number, since it is larger than the sum of its proper divisors (7041312221).

21123936651 is an equidigital number, since it uses as much as digits as its factorization.

21123936651 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7041312220.

The product of its digits is 58320, while the sum is 39.

The spelling of 21123936651 in words is "twenty-one billion, one hundred twenty-three million, nine hundred thirty-six thousand, six hundred fifty-one".