21720020337 has 12 divisors (see below), whose sum is σ = 31374641220. Its totient is φ = 14479423488.

The previous prime is 21720020303. The next prime is 21720020341. The reversal of 21720020337 is 73302002712.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 20227666176 + 1492354161 = 142224^2 + 38631^2 .

It is not a de Polignac number, because 21720020337 - 2⁷ = 21720020209 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21720020337.

It is not an unprimeable number, because it can be changed into a prime (21720020737) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 397489 + ... + 448817.

It is an arithmetic number, because the mean of its divisors is an integer number (2614553435).

Almost surely, 2^21720020337 is an apocalyptic number.

It is an amenable number.

21720020337 is a deficient number, since it is larger than the sum of its proper divisors (9654620883).

21720020337 is a wasteful number, since it uses less digits than its factorization.

21720020337 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 98352 (or 98349 counting only the distinct ones).

The product of its (nonzero) digits is 3528, while the sum is 27.

The spelling of 21720020337 in words is "twenty-one billion, seven hundred twenty million, twenty thousand, three hundred thirty-seven".