21709491018 has 64 divisors (see below), whose sum is σ = 44550172800. Its totient is φ = 7050776832.

The previous prime is 21709491017. The next prime is 21709491019. The reversal of 21709491018 is 81019490712.

It is an interprime number because it is at equal distance from previous prime (21709491017) and next prime (21709491019).

It is not an unprimeable number, because it can be changed into a prime (21709491017) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 17549496 + ... + 17550732.

It is an arithmetic number, because the mean of its divisors is an integer number (696096450).

Almost surely, 2^21709491018 is an apocalyptic number.

21709491018 is an abundant number, since it is smaller than the sum of its proper divisors (22840681782).

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

21709491018 is a wasteful number, since it uses less digits than its factorization.

21709491018 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1751.

The product of its (nonzero) digits is 36288, while the sum is 42.

The spelling of 21709491018 in words is "twenty-one billion, seven hundred nine million, four hundred ninety-one thousand, eighteen".