21771906 has 16 divisors (see below), whose sum is σ = 46893504. Its totient is φ = 6699024.

The previous prime is 21771859. The next prime is 21771907. The reversal of 21771906 is 60917712.

It is not an unprimeable number, because it can be changed into a prime (21771907) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 139486 + ... + 139641.

It is an arithmetic number, because the mean of its divisors is an integer number (2930844).

Almost surely, 2^21771906 is an apocalyptic number.

21771906 is a gapful number since it is divisible by the number (26) formed by its first and last digit.

21771906 is an abundant number, since it is smaller than the sum of its proper divisors (25121598).

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

21771906 is a wasteful number, since it uses less digits than its factorization.

21771906 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 279145.

The product of its (nonzero) digits is 5292, while the sum is 33.

The square root of 21771906 is about 4666.0375052072. The cubic root of 21771906 is about 279.2321906738.

The spelling of 21771906 in words is "twenty-one million, seven hundred seventy-one thousand, nine hundred six".