21721157507 has 8 divisors (see below), whose sum is σ = 25495104096. Its totient is φ = 18114941952.

The previous prime is 21721157483. The next prime is 21721157539. The reversal of 21721157507 is 70575112712.

It is a happy number.

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

It is a cyclic number.

It is not a de Polignac number, because 21721157507 - 2⁶ = 21721157443 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21721157597) 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, 41932478 + ... + 41932995.

It is an arithmetic number, because the mean of its divisors is an integer number (3186888012).

Almost surely, 2^21721157507 is an apocalyptic number.

21721157507 is a deficient number, since it is larger than the sum of its proper divisors (3773946589).

21721157507 is an equidigital number, since it uses as much as digits as its factorization.

21721157507 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 83865517.

The product of its (nonzero) digits is 34300, while the sum is 38.

The spelling of 21721157507 in words is "twenty-one billion, seven hundred twenty-one million, one hundred fifty-seven thousand, five hundred seven".