21539839400402 has 4 divisors (see below), whose sum is σ = 32309759100606. Its totient is φ = 10769919700200.

The previous prime is 21539839400389. The next prime is 21539839400437. The reversal of 21539839400402 is 20400493893512.

It is a happy number.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in only one way, i.e., 18798632676121 + 2741206724281 = 4335739^2 + 1655659^2 .

It is a super-2 number, since 2×21539839400402² (a number of 27 digits) contains 22 as substring.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5384959850099 + ... + 5384959850102.

Almost surely, 2^{21539839400402} is an apocalyptic number.

21539839400402 is a deficient number, since it is larger than the sum of its proper divisors (10769919700204).

21539839400402 is a wasteful number, since it uses less digits than its factorization.

21539839400402 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10769919700203.

The product of its (nonzero) digits is 1866240, while the sum is 50.

The spelling of 21539839400402 in words is "twenty-one trillion, five hundred thirty-nine billion, eight hundred thirty-nine million, four hundred thousand, four hundred two".