21709243640 has 64 divisors (see below), whose sum is σ = 56738957760. Its totient is φ = 7321144320.

The previous prime is 21709243631. The next prime is 21709243643. The reversal of 21709243640 is 4634290712.

It is a hoax number, since the sum of its digits (38) coincides with the sum of the digits of its distinct prime factors.

It is a junction number, because it is equal to n+sod(n) for n = 21709243594 and 21709243603.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21709243643) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 618437 + ... + 652596.

It is an arithmetic number, because the mean of its divisors is an integer number (886546215).

Almost surely, 2^21709243640 is an apocalyptic number.

21709243640 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21709243640 is an abundant number, since it is smaller than the sum of its proper divisors (35029714120).

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

21709243640 is a wasteful number, since it uses less digits than its factorization.

21709243640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1271112 (or 1271108 counting only the distinct ones).

The product of its (nonzero) digits is 72576, while the sum is 38.

The spelling of 21709243640 in words is "twenty-one billion, seven hundred nine million, two hundred forty-three thousand, six hundred forty".