21538464 has 24 divisors (see below), whose sum is σ = 56538720. Its totient is φ = 7179456.

The previous prime is 21538463. The next prime is 21538471. The reversal of 21538464 is 46483512.

It is a tau number, because it is divible by the number of its divisors (24).

It is not an unprimeable number, because it can be changed into a prime (21538463) 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, 112084 + ... + 112275.

It is an arithmetic number, because the mean of its divisors is an integer number (2355780).

Almost surely, 2^21538464 is an apocalyptic number.

21538464 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

21538464 is an abundant number, since it is smaller than the sum of its proper divisors (35000256).

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

21538464 is a wasteful number, since it uses less digits than its factorization.

21538464 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 224372 (or 224364 counting only the distinct ones).

The product of its digits is 23040, while the sum is 33.

The square root of 21538464 is about 4640.9550741200. The cubic root of 21538464 is about 278.2306110553.

It can be divided in two parts, 2153846 and 4, that added together give a triangular number (2153850 = T₂₀₇₅).

The spelling of 21538464 in words is "twenty-one million, five hundred thirty-eight thousand, four hundred sixty-four".