21661020023 has 8 divisors (see below), whose sum is σ = 22071969936. Its totient is φ = 21250153600.

The previous prime is 21661020013. The next prime is 21661020061. The reversal of 21661020023 is 32002016612.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21661020023 - 2¹² = 21661015927 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21661020013) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 822368 + ... + 848298.

It is an arithmetic number, because the mean of its divisors is an integer number (2758996242).

Almost surely, 2^21661020023 is an apocalyptic number.

21661020023 is a deficient number, since it is larger than the sum of its proper divisors (410949913).

21661020023 is a wasteful number, since it uses less digits than its factorization.

21661020023 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 41745.

The product of its (nonzero) digits is 864, while the sum is 23.

Adding to 21661020023 its reverse (32002016612), we get a palindrome (53663036635).

The spelling of 21661020023 in words is "twenty-one billion, six hundred sixty-one million, twenty thousand, twenty-three".