21212001240 has 64 divisors (see below), whose sum is σ = 64402732800. Its totient is φ = 5588380032.

The previous prime is 21212001233. The next prime is 21212001241. The reversal of 21212001240 is 4210021212.

It is a Harshad number since it is a multiple of its sum of digits (15).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21212001241) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1054900 + ... + 1074819.

It is an arithmetic number, because the mean of its divisors is an integer number (1006292700).

Almost surely, 2^21212001240 is an apocalyptic number.

21212001240 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21212001240 is an abundant number, since it is smaller than the sum of its proper divisors (43190731560).

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

21212001240 is a wasteful number, since it uses less digits than its factorization.

21212001240 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2129816 (or 2129812 counting only the distinct ones).

The product of its (nonzero) digits is 64, while the sum is 15.

Adding to 21212001240 its reverse (4210021212), we get a palindrome (25422022452).

The spelling of 21212001240 in words is "twenty-one billion, two hundred twelve million, one thousand, two hundred forty".