20991513312 has 192 divisors, whose sum is σ = 76333017600. Its totient is φ = 5452323840.

The previous prime is 20991513287. The next prime is 20991513331. The reversal of 20991513312 is 21331519902.

20991513312 is a `hidden beast` number, since 20 + 9 + 91 + 513 + 31 + 2 = 666.

It is a super-2 number, since 2×20991513312² (a number of 21 digits) contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 91237 + ... + 224292.

It is an arithmetic number, because the mean of its divisors is an integer number (397567800).

Almost surely, 2^20991513312 is an apocalyptic number.

20991513312 is a gapful number since it is divisible by the number (22) formed by its first and last digit.

It is an amenable number.

20991513312 is an abundant number, since it is smaller than the sum of its proper divisors (55341504288).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

20991513312 is a wasteful number, since it uses less digits than its factorization.

20991513312 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 315566 (or 315552 counting only the distinct ones).

The product of its (nonzero) digits is 14580, while the sum is 36.

The spelling of 20991513312 in words is "twenty billion, nine hundred ninety-one million, five hundred thirteen thousand, three hundred twelve".