21978085149 has 6 divisors (see below), whose sum is σ = 31746123006. Its totient is φ = 14652056760.

The previous prime is 21978085139. The next prime is 21978085169. The reversal of 21978085149 is 94158087912.

It is a happy number.

It can be written as a sum of positive squares in only one way, i.e., 19754302500 + 2223782649 = 140550^2 + 47157^2 .

It is not a de Polignac number, because 21978085149 - 2¹² = 21978081053 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21978085095 and 21978085104.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21978085139) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1221004722 + ... + 1221004739.

It is an arithmetic number, because the mean of its divisors is an integer number (5291020501).

Almost surely, 2^21978085149 is an apocalyptic number.

It is an amenable number.

21978085149 is a deficient number, since it is larger than the sum of its proper divisors (9768037857).

21978085149 is a wasteful number, since it uses less digits than its factorization.

21978085149 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2442009467 (or 2442009464 counting only the distinct ones).

The product of its (nonzero) digits is 1451520, while the sum is 54.

The spelling of 21978085149 in words is "twenty-one billion, nine hundred seventy-eight million, eighty-five thousand, one hundred forty-nine".