21661020450431 has 16 divisors (see below), whose sum is σ = 22015225651200. Its totient is φ = 21307741918848.

The previous prime is 21661020450379. The next prime is 21661020450437. The reversal of 21661020450431 is 13405402016612.

It is a cyclic number.

It is not a de Polignac number, because 21661020450431 - 2¹⁰ = 21661020449407 is a prime.

It is a super-2 number, since 2×21661020450431² (a number of 27 digits) contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21661020450391 and 21661020450400.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21661020450437) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 166170626 + ... + 166300928.

It is an arithmetic number, because the mean of its divisors is an integer number (1375951603200).

Almost surely, 2^{21661020450431} is an apocalyptic number.

21661020450431 is a deficient number, since it is larger than the sum of its proper divisors (354205200769).

21661020450431 is a wasteful number, since it uses less digits than its factorization.

21661020450431 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 133838.

The product of its (nonzero) digits is 34560, while the sum is 35.

The spelling of 21661020450431 in words is "twenty-one trillion, six hundred sixty-one billion, twenty million, four hundred fifty thousand, four hundred thirty-one".