821647801971 has 16 divisors (see below), whose sum is σ = 1270180177920. Its totient is φ = 523949322600.

The previous prime is 821647801951. The next prime is 821647801981. The reversal of 821647801971 is 179108746128.

821647801971 is a `hidden beast` number, since 82 + 1 + 6 + 478 + 0 + 1 + 97 + 1 = 666.

It is not a de Polignac number, because 821647801971 - 2³¹ = 819500318323 is a prime.

It is a super-2 number, since 2×821647801971² (a number of 25 digits) contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (821647801951) 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, 661551555 + ... + 661552796.

It is an arithmetic number, because the mean of its divisors is an integer number (79386261120).

Almost surely, 2^821647801971 is an apocalyptic number.

821647801971 is a deficient number, since it is larger than the sum of its proper divisors (448532375949).

821647801971 is a wasteful number, since it uses less digits than its factorization.

821647801971 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1323104383 (or 1323104377 counting only the distinct ones).

The product of its (nonzero) digits is 1354752, while the sum is 54.

The spelling of 821647801971 in words is "eight hundred twenty-one billion, six hundred forty-seven million, eight hundred one thousand, nine hundred seventy-one".