20151016821 has 36 divisors (see below), whose sum is σ = 32464354468. Its totient is φ = 11972959488.

The previous prime is 20151016819. The next prime is 20151016829. The reversal of 20151016821 is 12861015102.

It can be written as a sum of positive squares in 6 ways, for example, as 238702500 + 19912314321 = 15450^2 + 141111^2 .

It is not a de Polignac number, because 20151016821 - 2¹ = 20151016819 is a prime.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20151016829) by changing a digit.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 4000 + ... + 200793.

Almost surely, 2^20151016821 is an apocalyptic number.

It is an amenable number.

20151016821 is a deficient number, since it is larger than the sum of its proper divisors (12313337647).

20151016821 is a wasteful number, since it uses less digits than its factorization.

20151016821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 204870 (or 204838 counting only the distinct ones).

The product of its (nonzero) digits is 960, while the sum is 27.

The spelling of 20151016821 in words is "twenty billion, one hundred fifty-one million, sixteen thousand, eight hundred twenty-one".