71687821 has 2 divisors, whose sum is σ = 71687822. Its totient is φ = 71687820.

The previous prime is 71687813. The next prime is 71687843. The reversal of 71687821 is 12878617.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 64979721 + 6708100 = 8061^2 + 2590^2 .

It is a cyclic number.

It is not a de Polignac number, because 71687821 - 2³ = 71687813 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (71687621) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 35843910 + 35843911.

It is an arithmetic number, because the mean of its divisors is an integer number (35843911).

Almost surely, 2^71687821 is an apocalyptic number.

It is an amenable number.

71687821 is a deficient number, since it is larger than the sum of its proper divisors (1).

71687821 is an equidigital number, since it uses as much as digits as its factorization.

71687821 is an evil number, because the sum of its binary digits is even.

The product of its digits is 37632, while the sum is 40.

The square root of 71687821 is about 8466.8660672057. The cubic root of 71687821 is about 415.4146356702.

The spelling of 71687821 in words is "seventy-one million, six hundred eighty-seven thousand, eight hundred twenty-one".