21537717081 has 8 divisors (see below), whose sum is σ = 28720120704. Its totient is φ = 14356895760.

The previous prime is 21537717079. The next prime is 21537717107. The reversal of 21537717081 is 18071773512.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21537717081 - 2¹ = 21537717079 is a prime.

It is a super-2 number, since 2×21537717081² (a number of 21 digits) contains 22 as substring.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21537717031) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 363441 + ... + 418526.

It is an arithmetic number, because the mean of its divisors is an integer number (3590015088).

Almost surely, 2^21537717081 is an apocalyptic number.

It is an amenable number.

21537717081 is a deficient number, since it is larger than the sum of its proper divisors (7182403623).

21537717081 is an equidigital number, since it uses as much as digits as its factorization.

21537717081 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 791151.

The product of its (nonzero) digits is 82320, while the sum is 42.

The spelling of 21537717081 in words is "twenty-one billion, five hundred thirty-seven million, seven hundred seventeen thousand, eighty-one".