21006440940 has 24 divisors (see below), whose sum is σ = 58818034800. Its totient is φ = 5601717568.

The previous prime is 21006440927. The next prime is 21006440947. The reversal of 21006440940 is 4904460012.

It is a Harshad number since it is a multiple of its sum of digits (30).

It is a junction number, because it is equal to n+sod(n) for n = 21006440898 and 21006440907.

It is not an unprimeable number, because it can be changed into a prime (21006440947) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 175053615 + ... + 175053734.

It is an arithmetic number, because the mean of its divisors is an integer number (2450751450).

Almost surely, 2^21006440940 is an apocalyptic number.

21006440940 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21006440940 is an abundant number, since it is smaller than the sum of its proper divisors (37811593860).

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

21006440940 is a wasteful number, since it uses less digits than its factorization.

21006440940 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 350107361 (or 350107359 counting only the distinct ones).

The product of its (nonzero) digits is 6912, while the sum is 30.

The spelling of 21006440940 in words is "twenty-one billion, six million, four hundred forty thousand, nine hundred forty".