21084397651 has 4 divisors (see below), whose sum is σ = 21084688872. Its totient is φ = 21084106432.

The previous prime is 21084397639. The next prime is 21084397673. The reversal of 21084397651 is 15679348012.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21084397651 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21084397051) 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, 56520 + ... + 212986.

It is an arithmetic number, because the mean of its divisors is an integer number (5271172218).

It is a 2-persistent number, because it is pandigital, and so is 2⋅21084397651 = 42168795302, but 3⋅21084397651 = 63253192953 is not.

Almost surely, 2^21084397651 is an apocalyptic number.

21084397651 is the 91836-th centered pentagonal number.

21084397651 is a deficient number, since it is larger than the sum of its proper divisors (291221).

21084397651 is a wasteful number, since it uses less digits than its factorization.

21084397651 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 291220.

The product of its (nonzero) digits is 362880, while the sum is 46.

The spelling of 21084397651 in words is "twenty-one billion, eighty-four million, three hundred ninety-seven thousand, six hundred fifty-one".