820126989721 has 8 divisors (see below), whose sum is σ = 888093317384. Its totient is φ = 752857752960.

The previous prime is 820126989697. The next prime is 820126989793. The reversal of 820126989721 is 127989621028.

It can be written as a sum of positive squares in 4 ways, for example, as 28311764121 + 791815225600 = 168261^2 + 889840^2 .

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 820126989721 - 2²⁷ = 819992771993 is a prime.

It is not an unprimeable number, because it can be changed into a prime (820126989221) 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, 174270276 + ... + 174274981.

It is an arithmetic number, because the mean of its divisors is an integer number (111011664673).

Almost surely, 2^820126989721 is an apocalyptic number.

It is an amenable number.

820126989721 is a deficient number, since it is larger than the sum of its proper divisors (67966327663).

820126989721 is a wasteful number, since it uses less digits than its factorization.

820126989721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 348545451.

The product of its (nonzero) digits is 1741824, while the sum is 55.

The spelling of 820126989721 in words is "eight hundred twenty billion, one hundred twenty-six million, nine hundred eighty-nine thousand, seven hundred twenty-one".