21617972 has 12 divisors (see below), whose sum is σ = 39822720. Its totient is φ = 10240056.

The previous prime is 21617969. The next prime is 21617977. The reversal of 21617972 is 27971612.

It is a super-4 number, since 4×21617972⁴ (a number of 30 digits) contains 4444 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21617977) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 142148 + ... + 142299.

It is an arithmetic number, because the mean of its divisors is an integer number (3318560).

Almost surely, 2^21617972 is an apocalyptic number.

It is an amenable number.

21617972 is a deficient number, since it is larger than the sum of its proper divisors (18204748).

21617972 is a wasteful number, since it uses less digits than its factorization.

21617972 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 284470 (or 284468 counting only the distinct ones).

The product of its digits is 10584, while the sum is 35.

The square root of 21617972 is about 4649.5130927872. The cubic root of 21617972 is about 278.5725480810.

The spelling of 21617972 in words is "twenty-one million, six hundred seventeen thousand, nine hundred seventy-two".