21421040 has 20 divisors (see below), whose sum is σ = 49804104. Its totient is φ = 8568384.

The previous prime is 21420991. The next prime is 21421051. The reversal of 21421040 is 4012412.

It is a tau number, because it is divible by the number of its divisors (20).

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, 133802 + ... + 133961.

Almost surely, 2^21421040 is an apocalyptic number.

21421040 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21421040 is an abundant number, since it is smaller than the sum of its proper divisors (28383064).

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

21421040 is a wasteful number, since it uses less digits than its factorization.

21421040 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 267776 (or 267770 counting only the distinct ones).

The product of its (nonzero) digits is 64, while the sum is 14.

The square root of 21421040 is about 4628.2869401108. The cubic root of 21421040 is about 277.7240676006.

Adding to 21421040 its reverse (4012412), we get a palindrome (25433452).

The spelling of 21421040 in words is "twenty-one million, four hundred twenty-one thousand, forty".