21977946 has 64 divisors (see below), whose sum is σ = 53145600. Its totient is φ = 6706800.

The previous prime is 21977941. The next prime is 21977953. The reversal of 21977946 is 64977912.

It is a super-2 number, since 2×21977946² = 966060220757832, which contains 22 as substring.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21977941) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 31461 + ... + 32151.

It is an arithmetic number, because the mean of its divisors is an integer number (830400).

Almost surely, 2^21977946 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21977946, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (26572800).

21977946 is an abundant number, since it is smaller than the sum of its proper divisors (31167654).

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

21977946 is a wasteful number, since it uses less digits than its factorization.

21977946 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 752 (or 746 counting only the distinct ones).

The product of its digits is 190512, while the sum is 45.

The square root of 21977946 is about 4688.0642060450. The cubic root of 21977946 is about 280.1102711925.

The spelling of 21977946 in words is "twenty-one million, nine hundred seventy-seven thousand, nine hundred forty-six".