21951378 has 16 divisors (see below), whose sum is σ = 48780960. Its totient is φ = 7317108.

The previous prime is 21951367. The next prime is 21951383. The reversal of 21951378 is 87315912.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 203200 + ... + 203307.

It is an arithmetic number, because the mean of its divisors is an integer number (3048810).

Almost surely, 2^21951378 is an apocalyptic number.

21951378 is an abundant number, since it is smaller than the sum of its proper divisors (26829582).

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

21951378 is a wasteful number, since it uses less digits than its factorization.

21951378 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 406518 (or 406512 counting only the distinct ones).

The product of its digits is 15120, while the sum is 36.

The square root of 21951378 is about 4685.2297702461. The cubic root of 21951378 is about 279.9973554172.

The spelling of 21951378 in words is "twenty-one million, nine hundred fifty-one thousand, three hundred seventy-eight".