21311955 has 48 divisors (see below), whose sum is σ = 43692480. Its totient is φ = 9402624.

The previous prime is 21311951. The next prime is 21311957. The reversal of 21311955 is 55911312.

It is not a de Polignac number, because 21311955 - 2² = 21311951 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21311951) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 7969 + ... + 10301.

It is an arithmetic number, because the mean of its divisors is an integer number (910260).

Almost surely, 2^21311955 is an apocalyptic number.

21311955 is an abundant number, since it is smaller than the sum of its proper divisors (22380525).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21311955 is a wasteful number, since it uses less digits than its factorization.

21311955 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2380 (or 2377 counting only the distinct ones).

The product of its digits is 1350, while the sum is 27.

The square root of 21311955 is about 4616.4873009681. The cubic root of 21311955 is about 277.2518355990.

The spelling of 21311955 in words is "twenty-one million, three hundred eleven thousand, nine hundred fifty-five".