21378135473 has 4 divisors (see below), whose sum is σ = 22307619648. Its totient is φ = 20448651300.

The previous prime is 21378135403. The next prime is 21378135479. The reversal of 21378135473 is 37453187312.

It is a happy number.

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 21378135473 - 2¹² = 21378131377 is a prime.

It is a super-3 number, since 3×21378135473³ (a number of 32 digits) contains 333 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21378135479) 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, 464742053 + ... + 464742098.

It is an arithmetic number, because the mean of its divisors is an integer number (5576904912).

Almost surely, 2^21378135473 is an apocalyptic number.

21378135473 is a gapful number since it is divisible by the number (23) formed by its first and last digit.

It is an amenable number.

21378135473 is a deficient number, since it is larger than the sum of its proper divisors (929484175).

21378135473 is an equidigital number, since it uses as much as digits as its factorization.

21378135473 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 929484174.

The product of its digits is 423360, while the sum is 44.

The spelling of 21378135473 in words is "twenty-one billion, three hundred seventy-eight million, one hundred thirty-five thousand, four hundred seventy-three".