21531394 has 8 divisors (see below), whose sum is σ = 32514300. Its totient is φ = 10693296.

The previous prime is 21531379. The next prime is 21531439. The reversal of 21531394 is 49313512.

It can be written as a sum of positive squares in 2 ways, for example, as 19936225 + 1595169 = 4465^2 + 1263^2 .

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

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, 35829 + ... + 36424.

Almost surely, 2^21531394 is an apocalyptic number.

21531394 is a deficient number, since it is larger than the sum of its proper divisors (10982906).

21531394 is a wasteful number, since it uses less digits than its factorization.

21531394 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 72404.

The product of its digits is 3240, while the sum is 28.

The square root of 21531394 is about 4640.1933149385. The cubic root of 21531394 is about 278.2001646612.

The spelling of 21531394 in words is "twenty-one million, five hundred thirty-one thousand, three hundred ninety-four".