21540438 has 32 divisors (see below), whose sum is σ = 49165920. Its totient is φ = 6985440.

The previous prime is 21540437. The next prime is 21540439. The reversal of 21540438 is 83404512.

It is an interprime number because it is at equal distance from previous prime (21540437) and next prime (21540439).

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21540437) 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, 3393 + ... + 7388.

It is an arithmetic number, because the mean of its divisors is an integer number (1536435).

Almost surely, 2^21540438 is an apocalyptic number.

21540438 is an abundant number, since it is smaller than the sum of its proper divisors (27625482).

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

21540438 is a wasteful number, since it uses less digits than its factorization.

21540438 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10829 (or 10823 counting only the distinct ones).

The product of its (nonzero) digits is 3840, while the sum is 27.

The square root of 21540438 is about 4641.1677409893. The cubic root of 21540438 is about 278.2391107399.

The spelling of 21540438 in words is "twenty-one million, five hundred forty thousand, four hundred thirty-eight".