21231040 has 28 divisors (see below), whose sum is σ = 50557176. Its totient is φ = 8492288.

The previous prime is 21231029. The next prime is 21231107. The reversal of 21231040 is 4013212.

It is a self number, because there is not a number n which added to its sum of digits gives 21231040.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 32854 + ... + 33493.

Almost surely, 2^21231040 is an apocalyptic number.

21231040 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21231040 is an abundant number, since it is smaller than the sum of its proper divisors (29326136).

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

21231040 is an equidigital number, since it uses as much as digits as its factorization.

21231040 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 66364 (or 66354 counting only the distinct ones).

The product of its (nonzero) digits is 48, while the sum is 13.

The square root of 21231040 is about 4607.7152689809. The cubic root of 21231040 is about 276.9005103485.

Adding to 21231040 its reverse (4013212), we get a palindrome (25244252).

The spelling of 21231040 in words is "twenty-one million, two hundred thirty-one thousand, forty".