21378646977 has 4 divisors (see below), whose sum is σ = 28504862640. Its totient is φ = 14252431316.

The previous prime is 21378646951. The next prime is 21378646997. The reversal of 21378646977 is 77964687312.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21378646977 - 2¹⁴ = 21378630593 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21378646977.

It is not an unprimeable number, because it can be changed into a prime (21378646997) 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, 3563107827 + ... + 3563107832.

It is an arithmetic number, because the mean of its divisors is an integer number (7126215660).

Almost surely, 2^21378646977 is an apocalyptic number.

It is an amenable number.

21378646977 is a deficient number, since it is larger than the sum of its proper divisors (7126215663).

21378646977 is an equidigital number, since it uses as much as digits as its factorization.

21378646977 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7126215662.

The product of its digits is 21337344, while the sum is 60.

The spelling of 21378646977 in words is "twenty-one billion, three hundred seventy-eight million, six hundred forty-six thousand, nine hundred seventy-seven".