21461240 has 16 divisors (see below), whose sum is σ = 48287880. Its totient is φ = 8584480.

The previous prime is 21461233. The next prime is 21461249. The reversal of 21461240 is 4216412.

It is a Harshad number since it is a multiple of its sum of digits (20).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21461249) 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, 268226 + ... + 268305.

Almost surely, 2^21461240 is an apocalyptic number.

21461240 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21461240 is an abundant number, since it is smaller than the sum of its proper divisors (26826640).

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

21461240 is a wasteful number, since it uses less digits than its factorization.

21461240 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 536542 (or 536538 counting only the distinct ones).

The product of its (nonzero) digits is 384, while the sum is 20.

The square root of 21461240 is about 4632.6277640234. The cubic root of 21461240 is about 277.8976902134.

Adding to 21461240 its reverse (4216412), we get a palindrome (25677652).

The spelling of 21461240 in words is "twenty-one million, four hundred sixty-one thousand, two hundred forty".