21407538 has 8 divisors (see below), whose sum is σ = 42815088. Its totient is φ = 7135844.

The previous prime is 21407537. The next prime is 21407543. The reversal of 21407538 is 83570412.

It is a sphenic number, since it is the product of 3 distinct primes.

21407538 is an admirable number.

It is not an unprimeable number, because it can be changed into a prime (21407531) 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, 1783956 + ... + 1783967.

It is an arithmetic number, because the mean of its divisors is an integer number (5351886).

Almost surely, 2^21407538 is an apocalyptic number.

21407538 is a primitive abundant number, since it is smaller than the sum of its proper divisors, none of which is abundant.

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

21407538 is a wasteful number, since it uses less digits than its factorization.

21407538 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3567928.

The product of its (nonzero) digits is 6720, while the sum is 30.

The square root of 21407538 is about 4626.8280711520. The cubic root of 21407538 is about 277.6657041335.

It can be divided in two parts, 21407 and 538, that added together give a triangular number (21945 = T₂₀₉).

The spelling of 21407538 in words is "twenty-one million, four hundred seven thousand, five hundred thirty-eight".