21997436 has 12 divisors (see below), whose sum is σ = 38537520. Its totient is φ = 10986720.

The previous prime is 21997429. The next prime is 21997441. The reversal of 21997436 is 63479912.

It is a junction number, because it is equal to n+sod(n) for n = 21997393 and 21997402.

It is a congruent number.

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, 2081 + ... + 6951.

It is an arithmetic number, because the mean of its divisors is an integer number (3211460).

Almost surely, 2^21997436 is an apocalyptic number.

It is an amenable number.

21997436 is a deficient number, since it is larger than the sum of its proper divisors (16540084).

21997436 is a wasteful number, since it uses less digits than its factorization.

21997436 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6004 (or 6002 counting only the distinct ones).

The product of its digits is 81648, while the sum is 41.

The square root of 21997436 is about 4690.1424285409. The cubic root of 21997436 is about 280.1930471444.

The spelling of 21997436 in words is "twenty-one million, nine hundred ninety-seven thousand, four hundred thirty-six".