21506898816 has 128 divisors (see below), whose sum is σ = 68358074400. Its totient is φ = 6617493504.

The previous prime is 21506898797. The next prime is 21506898839. The reversal of 21506898816 is 61889860512.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (128).

It is a super-4 number, since 4×21506898816⁴ (a number of 42 digits) contains 4444 as substring.

It is a Harshad number since it is a multiple of its sum of digits (54).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 194421 + ... + 284276.

Almost surely, 2^21506898816 is an apocalyptic number.

21506898816 is a gapful number since it is divisible by the number (26) formed by its first and last digit.

It is an amenable number.

21506898816 is an abundant number, since it is smaller than the sum of its proper divisors (46851175584).

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

21506898816 is a wasteful number, since it uses less digits than its factorization.

21506898816 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 478733 (or 478715 counting only the distinct ones).

The product of its (nonzero) digits is 1658880, while the sum is 54.

The spelling of 21506898816 in words is "twenty-one billion, five hundred six million, eight hundred ninety-eight thousand, eight hundred sixteen".