21397772 has 12 divisors (see below), whose sum is σ = 40850376. Its totient is φ = 9726240.

The previous prime is 21397771. The next prime is 21397787. The reversal of 21397772 is 27779312.

It is not an unprimeable number, because it can be changed into a prime (21397771) 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, 243113 + ... + 243200.

It is an arithmetic number, because the mean of its divisors is an integer number (3404198).

Almost surely, 2^21397772 is an apocalyptic number.

21397772 is a gapful number since it is divisible by the number (22) formed by its first and last digit.

It is an amenable number.

21397772 is a deficient number, since it is larger than the sum of its proper divisors (19452604).

21397772 is a wasteful number, since it uses less digits than its factorization.

21397772 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 486328 (or 486326 counting only the distinct ones).

The product of its digits is 37044, while the sum is 38.

The square root of 21397772 is about 4625.7725841204. The cubic root of 21397772 is about 277.6234745269.

It can be divided in two parts, 21 and 397772, that added together give a palindrome (397793).

The spelling of 21397772 in words is "twenty-one million, three hundred ninety-seven thousand, seven hundred seventy-two".