21661634420 has 48 divisors (see below), whose sum is σ = 46572926400. Its totient is φ = 8458496256.

The previous prime is 21661634329. The next prime is 21661634441. The reversal of 21661634420 is 2443616612.

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, 1845731 + ... + 1857429.

It is an arithmetic number, because the mean of its divisors is an integer number (970269300).

Almost surely, 2^21661634420 is an apocalyptic number.

21661634420 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21661634420 is an abundant number, since it is smaller than the sum of its proper divisors (24911291980).

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

21661634420 is a wasteful number, since it uses less digits than its factorization.

21661634420 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 13904 (or 13902 counting only the distinct ones).

The product of its (nonzero) digits is 41472, while the sum is 35.

The spelling of 21661634420 in words is "twenty-one billion, six hundred sixty-one million, six hundred thirty-four thousand, four hundred twenty".