21693506 has 8 divisors (see below), whose sum is σ = 32759100. Its totient is φ = 10773808.

The previous prime is 21693499. The next prime is 21693509. The reversal of 21693506 is 60539612.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 21077281 + 616225 = 4591^2 + 785^2 .

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

It is not an unprimeable number, because it can be changed into a prime (21693509) 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, 36101 + ... + 36696.

Almost surely, 2^21693506 is an apocalyptic number.

21693506 is a deficient number, since it is larger than the sum of its proper divisors (11065594).

21693506 is a wasteful number, since it uses less digits than its factorization.

21693506 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 72948.

The product of its (nonzero) digits is 9720, while the sum is 32.

The square root of 21693506 is about 4657.6287958574. The cubic root of 21693506 is about 278.8966185578.

The spelling of 21693506 in words is "twenty-one million, six hundred ninety-three thousand, five hundred six".