21764207538 has 12 divisors (see below), whose sum is σ = 47155783038. Its totient is φ = 7254735840.

The previous prime is 21764207537. The next prime is 21764207579. The reversal of 21764207538 is 83570246712.

21764207538 is a `hidden beast` number, since 2 + 1 + 76 + 42 + 0 + 7 + 538 = 666.

It can be written as a sum of positive squares in only one way, i.e., 16089146649 + 5675060889 = 126843^2 + 75333^2 .

It is a super-3 number, since 3×21764207538³ (a number of 32 digits) contains 333 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21764207493 and 21764207502.

It is not an unprimeable number, because it can be changed into a prime (21764207537) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 604561303 + ... + 604561338.

Almost surely, 2^21764207538 is an apocalyptic number.

21764207538 is an abundant number, since it is smaller than the sum of its proper divisors (25391575500).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21764207538 is a wasteful number, since it uses less digits than its factorization.

21764207538 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1209122649 (or 1209122646 counting only the distinct ones).

The product of its (nonzero) digits is 564480, while the sum is 45.

The spelling of 21764207538 in words is "twenty-one billion, seven hundred sixty-four million, two hundred seven thousand, five hundred thirty-eight".