20370721 has 6 divisors (see below), whose sum is σ = 23696610. Its totient is φ = 17460576.

The previous prime is 20370719. The next prime is 20370739. The reversal of 20370721 is 12707302.

It can be written as a sum of positive squares in only one way, i.e., 18835600 + 1535121 = 4340^2 + 1239^2 .

It is not a de Polignac number, because 20370721 - 2¹ = 20370719 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 20370692 and 20370701.

It is not an unprimeable number, because it can be changed into a prime (20370761) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 207816 + ... + 207913.

It is an arithmetic number, because the mean of its divisors is an integer number (3949435).

Almost surely, 2^20370721 is an apocalyptic number.

It is an amenable number.

20370721 is a deficient number, since it is larger than the sum of its proper divisors (3325889).

20370721 is an equidigital number, since it uses as much as digits as its factorization.

20370721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 415743 (or 415736 counting only the distinct ones).

The product of its (nonzero) digits is 588, while the sum is 22.

The square root of 20370721 is about 4513.3935126466. The cubic root of 20370721 is about 273.1086571638.

The spelling of 20370721 in words is "twenty million, three hundred seventy thousand, seven hundred twenty-one".