21993693 has 16 divisors (see below), whose sum is σ = 29927040. Its totient is φ = 14364864.

The previous prime is 21993691. The next prime is 21993703. The reversal of 21993693 is 39639912.

It is a happy number.

It is not a de Polignac number, because 21993693 - 2¹ = 21993691 is a prime.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21993691) 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, 33355 + ... + 34007.

It is an arithmetic number, because the mean of its divisors is an integer number (1870440).

Almost surely, 2^21993693 is an apocalyptic number.

It is an amenable number.

21993693 is a deficient number, since it is larger than the sum of its proper divisors (7933347).

21993693 is a wasteful number, since it uses less digits than its factorization.

21993693 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 868.

The product of its digits is 78732, while the sum is 42.

The square root of 21993693 is about 4689.7433831714. The cubic root of 21993693 is about 280.1771540487.

The spelling of 21993693 in words is "twenty-one million, nine hundred ninety-three thousand, six hundred ninety-three".