21392091 has 12 divisors (see below), whose sum is σ = 35314032. Its totient is φ = 12224016.

The previous prime is 21392071. The next prime is 21392099. The reversal of 21392091 is 19029312.

It is not a de Polignac number, because 21392091 - 2¹¹ = 21390043 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21392099) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 169716 + ... + 169841.

It is an arithmetic number, because the mean of its divisors is an integer number (2942836).

Almost surely, 2^21392091 is an apocalyptic number.

21392091 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

21392091 is a deficient number, since it is larger than the sum of its proper divisors (13921941).

21392091 is a wasteful number, since it uses less digits than its factorization.

21392091 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 339570 (or 339567 counting only the distinct ones).

The product of its (nonzero) digits is 972, while the sum is 27.

The square root of 21392091 is about 4625.1584837711. The cubic root of 21392091 is about 277.5989031438.

The spelling of 21392091 in words is "twenty-one million, three hundred ninety-two thousand, ninety-one".