21391478020 has 24 divisors (see below), whose sum is σ = 49005931968. Its totient is φ = 7778719200.

The previous prime is 21391477999. The next prime is 21391478023. The reversal of 21391478020 is 2087419312.

It is not an unprimeable number, because it can be changed into a prime (21391478023) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 48616776 + ... + 48617215.

It is an arithmetic number, because the mean of its divisors is an integer number (2041913832).

Almost surely, 2^21391478020 is an apocalyptic number.

21391478020 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21391478020 is an abundant number, since it is smaller than the sum of its proper divisors (27614453948).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21391478020 is a wasteful number, since it uses less digits than its factorization.

21391478020 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 97234011 (or 97234009 counting only the distinct ones).

The product of its (nonzero) digits is 24192, while the sum is 37.

The spelling of 21391478020 in words is "twenty-one billion, three hundred ninety-one million, four hundred seventy-eight thousand, twenty".