21972006 has 64 divisors (see below), whose sum is σ = 57346560. Its totient is φ = 6104160.

The previous prime is 21971981. The next prime is 21972029. The reversal of 21972006 is 60027912.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a congruent number.

It is an unprimeable number.

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 31 ways as a sum of consecutive naturals, for example, 13201 + ... + 14771.

It is an arithmetic number, because the mean of its divisors is an integer number (896040).

Almost surely, 2^21972006 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21972006, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28673280).

21972006 is an abundant number, since it is smaller than the sum of its proper divisors (35374554).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21972006 is a wasteful number, since it uses less digits than its factorization.

21972006 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1626 (or 1620 counting only the distinct ones).

The product of its (nonzero) digits is 1512, while the sum is 27.

The square root of 21972006 is about 4687.4306394868. The cubic root of 21972006 is about 280.0850336972.

Adding to 21972006 its reverse (60027912), we get a palindrome (81999918).

The spelling of 21972006 in words is "twenty-one million, nine hundred seventy-two thousand, six".