21877029721 has 2 divisors, whose sum is σ = 21877029722. Its totient is φ = 21877029720.

The previous prime is 21877029689. The next prime is 21877029767. The reversal of 21877029721 is 12792077812.

It is an a-pointer prime, because the next prime (21877029767) can be obtained adding 21877029721 to its sum of digits (46).

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 19132422400 + 2744607321 = 138320^2 + 52389^2 .

It is a cyclic number.

It is not a de Polignac number, because 21877029721 - 2⁵ = 21877029689 is a prime.

It is not a weakly prime, because it can be changed into another prime (21877029821) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10938514860 + 10938514861.

It is an arithmetic number, because the mean of its divisors is an integer number (10938514861).

Almost surely, 2^21877029721 is an apocalyptic number.

It is an amenable number.

21877029721 is a deficient number, since it is larger than the sum of its proper divisors (1).

21877029721 is an equidigital number, since it uses as much as digits as its factorization.

21877029721 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 197568, while the sum is 46.

The spelling of 21877029721 in words is "twenty-one billion, eight hundred seventy-seven million, twenty-nine thousand, seven hundred twenty-one".