21898621836 has 720 divisors, whose sum is σ = 77773301760. Its totient is φ = 5240401920.

The previous prime is 21898621831. The next prime is 21898621873. The reversal of 21898621836 is 63812689812.

21898621836 is a `hidden beast` number, since 2 + 1 + 8 + 9 + 8 + 621 + 8 + 3 + 6 = 666.

It is a super-2 number, since 2×21898621836² (a number of 21 digits) contains 22 as substring.

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

It is not an unprimeable number, because it can be changed into a prime (21898621831) by changing a digit.

It is a polite number, since it can be written in 239 ways as a sum of consecutive naturals, for example, 225758940 + ... + 225759036.

Almost surely, 2^21898621836 is an apocalyptic number.

21898621836 is a gapful number since it is divisible by the number (26) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21898621836, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (38886650880).

21898621836 is an abundant number, since it is smaller than the sum of its proper divisors (55874679924).

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

21898621836 is a wasteful number, since it uses less digits than its factorization.

21898621836 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 196 (or 172 counting only the distinct ones).

The product of its digits is 1990656, while the sum is 54.

The spelling of 21898621836 in words is "twenty-one billion, eight hundred ninety-eight million, six hundred twenty-one thousand, eight hundred thirty-six".