21697930 has 16 divisors (see below), whose sum is σ = 39460680. Its totient is φ = 8589312.

The previous prime is 21697927. The next prime is 21697937. The reversal of 21697930 is 3979612.

It can be written as a sum of positive squares in 4 ways, for example, as 16540489 + 5157441 = 4067^2 + 2271^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 21697930.

It is not an unprimeable number, because it can be changed into a prime (21697937) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 10215 + ... + 12154.

Almost surely, 2^21697930 is an apocalyptic number.

21697930 is a deficient number, since it is larger than the sum of its proper divisors (17762750).

21697930 is a wasteful number, since it uses less digits than its factorization.

21697930 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 22473.

The product of its (nonzero) digits is 20412, while the sum is 37.

The square root of 21697930 is about 4658.1036914178. The cubic root of 21697930 is about 278.9155759173.

The spelling of 21697930 in words is "twenty-one million, six hundred ninety-seven thousand, nine hundred thirty".