21311240 has 16 divisors (see below), whose sum is σ = 47950380. Its totient is φ = 8524480.

The previous prime is 21311237. The next prime is 21311249. The reversal of 21311240 is 4211312.

It can be written as a sum of positive squares in 2 ways, for example, as 17859076 + 3452164 = 4226^2 + 1858^2 .

It is not an unprimeable number, because it can be changed into a prime (21311249) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 266351 + ... + 266430.

Almost surely, 2^21311240 is an apocalyptic number.

21311240 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21311240 is an abundant number, since it is smaller than the sum of its proper divisors (26639140).

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

21311240 is a wasteful number, since it uses less digits than its factorization.

21311240 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 532792 (or 532788 counting only the distinct ones).

The product of its (nonzero) digits is 48, while the sum is 14.

The square root of 21311240 is about 4616.4098604868. The cubic root of 21311240 is about 277.2487350344.

Adding to 21311240 its reverse (4211312), we get a palindrome (25522552).

The spelling of 21311240 in words is "twenty-one million, three hundred eleven thousand, two hundred forty".