20657021 has 16 divisors (see below), whose sum is σ = 26196480. Its totient is φ = 15820080.

The previous prime is 20656991. The next prime is 20657027. The reversal of 20657021 is 12075602.

It is a cyclic number.

It is not a de Polignac number, because 20657021 - 2¹⁰ = 20655997 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20657027) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 2270 + ... + 6816.

It is an arithmetic number, because the mean of its divisors is an integer number (1637280).

Almost surely, 2^20657021 is an apocalyptic number.

It is an amenable number.

20657021 is a deficient number, since it is larger than the sum of its proper divisors (5539459).

20657021 is a wasteful number, since it uses less digits than its factorization.

20657021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4624.

The product of its (nonzero) digits is 840, while the sum is 23.

The square root of 20657021 is about 4544.9995599560. Note that the first 3 decimals coincide. The cubic root of 20657021 is about 274.3821766551.

The spelling of 20657021 in words is "twenty million, six hundred fifty-seven thousand, twenty-one".