20612721 has 16 divisors (see below), whose sum is σ = 29203200. Its totient is φ = 12887808.

The previous prime is 20612717. The next prime is 20612723. The reversal of 20612721 is 12721602.

It is not a de Polignac number, because 20612721 - 2² = 20612717 is a prime.

It is not an unprimeable number, because it can be changed into a prime (20612723) 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, 19320 + ... + 20358.

It is an arithmetic number, because the mean of its divisors is an integer number (1825200).

Almost surely, 2^20612721 is an apocalyptic number.

It is an amenable number.

20612721 is a deficient number, since it is larger than the sum of its proper divisors (8590479).

20612721 is a wasteful number, since it uses less digits than its factorization.

20612721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1448.

The product of its (nonzero) digits is 336, while the sum is 21.

The square root of 20612721 is about 4540.1234564712. The cubic root of 20612721 is about 274.1858942405.

The spelling of 20612721 in words is "twenty million, six hundred twelve thousand, seven hundred twenty-one".