21231551500 has 48 divisors (see below), whose sum is σ = 46394187840. Its totient is φ = 8488137600.

The previous prime is 21231551491. The next prime is 21231551521. The reversal of 21231551500 is 515513212.

It is a Harshad number since it is a multiple of its sum of digits (25).

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, 1034337 + ... + 1054663.

It is an arithmetic number, because the mean of its divisors is an integer number (966545580).

Almost surely, 2^21231551500 is an apocalyptic number.

21231551500 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21231551500 is an abundant number, since it is smaller than the sum of its proper divisors (25162636340).

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

21231551500 is a wasteful number, since it uses less digits than its factorization.

21231551500 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 22435 (or 22423 counting only the distinct ones).

The product of its (nonzero) digits is 1500, while the sum is 25.

The spelling of 21231551500 in words is "twenty-one billion, two hundred thirty-one million, five hundred fifty-one thousand, five hundred".