20921672 has 8 divisors (see below), whose sum is σ = 39228150. Its totient is φ = 10460832.

The previous prime is 20921657. The next prime is 20921689. The reversal of 20921672 is 27612902.

It can be written as a sum of positive squares in only one way, i.e., 20921476 + 196 = 4574^2 + 14^2 .

It is a tau number, because it is divible by the number of its divisors (8).

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1307597 + ... + 1307612.

Almost surely, 2^20921672 is an apocalyptic number.

It is an amenable number.

20921672 is a deficient number, since it is larger than the sum of its proper divisors (18306478).

20921672 is a wasteful number, since it uses less digits than its factorization.

20921672 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2615215 (or 2615211 counting only the distinct ones).

The product of its (nonzero) digits is 3024, while the sum is 29.

The square root of 20921672 is about 4574.0214253980. The cubic root of 20921672 is about 275.5489727972.

The spelling of 20921672 in words is "twenty million, nine hundred twenty-one thousand, six hundred seventy-two".