21980091 has 16 divisors (see below), whose sum is σ = 33920000. Its totient is φ = 12400128.

The previous prime is 21980053. The next prime is 21980117. The reversal of 21980091 is 19008912.

It is not a de Polignac number, because 21980091 - 2¹¹ = 21978043 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21980041) 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, 4966 + ... + 8283.

It is an arithmetic number, because the mean of its divisors is an integer number (2120000).

Almost surely, 2^21980091 is an apocalyptic number.

21980091 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

21980091 is a deficient number, since it is larger than the sum of its proper divisors (11939909).

21980091 is a wasteful number, since it uses less digits than its factorization.

21980091 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 13338.

The product of its (nonzero) digits is 1296, while the sum is 30.

The square root of 21980091 is about 4688.2929729274. The cubic root of 21980091 is about 280.1193836150.

The spelling of 21980091 in words is "twenty-one million, nine hundred eighty thousand, ninety-one".