20515664421 has 24 divisors (see below), whose sum is σ = 35355795840. Its totient is φ = 11723236056.

The previous prime is 20515664417. The next prime is 20515664423. The reversal of 20515664421 is 12446651502.

20515664421 is a `hidden beast` number, since 2 + 0 + 5 + 1 + 5 + 6 + 644 + 2 + 1 = 666.

It is not a de Polignac number, because 20515664421 - 2² = 20515664417 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20515664423) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 7752141 + ... + 7754786.

It is an arithmetic number, because the mean of its divisors is an integer number (1473158160).

Almost surely, 2^20515664421 is an apocalyptic number.

20515664421 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

It is an amenable number.

20515664421 is a deficient number, since it is larger than the sum of its proper divisors (14840131419).

20515664421 is a wasteful number, since it uses less digits than its factorization.

20515664421 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 15506950 (or 15506937 counting only the distinct ones).

The product of its (nonzero) digits is 57600, while the sum is 36.

The spelling of 20515664421 in words is "twenty billion, five hundred fifteen million, six hundred sixty-four thousand, four hundred twenty-one".