21395390661 has 24 divisors (see below), whose sum is σ = 31215841280. Its totient is φ = 14120368416.

The previous prime is 21395390641. The next prime is 21395390729. The reversal of 21395390661 is 16609359312.

21395390661 is a `hidden beast` number, since 21 + 39 + 539 + 0 + 6 + 61 = 666.

It is not a de Polignac number, because 21395390661 - 2¹³ = 21395382469 is a prime.

It is a hoax number, since the sum of its digits (45) coincides with the sum of the digits of its distinct prime factors.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21395390641) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 508995 + ... + 549423.

Almost surely, 2^21395390661 is an apocalyptic number.

It is an amenable number.

21395390661 is a deficient number, since it is larger than the sum of its proper divisors (9820450619).

21395390661 is a wasteful number, since it uses less digits than its factorization.

21395390661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 41025 (or 41022 counting only the distinct ones).

The product of its (nonzero) digits is 262440, while the sum is 45.

The spelling of 21395390661 in words is "twenty-one billion, three hundred ninety-five million, three hundred ninety thousand, six hundred sixty-one".